During the 90s, the two main consoles at constant war with each other were the Super Nintendo and the Sega Genesis. Many people at the time debated which one was the best, and the sales between them reflected a constant back-and-forth. Sega went on to release multiple accessories for the Genesis, giving it an edge on the market and hopefully enticing gamers to buy more Sega products. One of the add-ons to the Genesis in 1992 was the Sega CD, a CD-ROM drive attachment that enabled the Genesis to play games stored on CD-ROMs. However, the high price point of the attachment was a major hurdle for most customers, which eventually led to a loss of momentum in the console race with Nintendo.

Despite this, the Sega CD still managed to have a wide assortment of games that supported the accessory. A combination of enhanced ports and original titles kept some Sega fans interested in what was available. But eventually, over time, most gamers and Sega itself moved on from the Sega CD, focusing more on newer products of the time. Since then, some games within the Sega CD library have become more valuable as collectibles and are sold on the second-hand market. Here are five of the rarest Sega CD games that you may never get to own.

5 Earthworm Jim: Special Edition

Even more groovy

There are plenty of 90s gamers who remember the game Earthworm Jim for the Sega Genesis, as well as on the Super Nintendo. But a year after that game was released, a special edition of it came to the Sega CD with a few enhancements over the original release. Earthworm Jim: Special Edition is very similar to what players know from the Sega Genesis version, but with additional sections to some of the levels that extend them a bit more. This version of the game also comes with an exclusive level called Big Bruty, in which Jim must avoid a blind dinosaur-like creature that is on an old shipwreck. This level does not appear in any other version of the game, including the HD remake of Earthworm Jim that came out in 2010.

Earthworm Jim: Special Edition also includes an alternate ending that can be played when completing the game. Depending on whether a player finishes on the practice or difficult setting, a narrator will give false facts about earthworms during the credits. Aside from these changes, the majority of the game remains unchanged from previous releases. Today, a loose copy of Earthworm Jim: Special Edition for Sega CD can be worth around $220 alone. However, if you manage to find it in its original box, containing all its contents, the price can range from $350 to $600 in some auctions.

4 Wonder Dog (Red Version)

A wonderful collectible

A long-forgotten mascot from the 90s is Wonder Dog, who appeared in a variety of materials for JVC back in that era. Wonder Dog is a game that plays like a 2D platformer, very similar to Super Mario Bros. on the NES, and has a lot of colorful visuals and a lighthearted tone. The plot of the game involves Wonder Dog trying to save the planet K-9 from a group of villainous dogs called the Pitbullies. For most people, this was a common approach for new mascots to appeal to a younger crowd and families, but it didn't help Wonder Dog remain relevant long after. The game received a lot of mixed reviews over time, despite having some positive reception when it first released. This game would also be the only time that the company JVC would try to get into the game console market in any significant way.

There are multiple versions of Wonder Dog for the Sega CD, a green box and a red box variant. The green box is the most common version that was found in 1993, while the red box is the first printing of the game in 1992, which was pulled from shelves after a short time. The red box version of Wonder Dog is more valuable to collectors, with loose copies of this version being valued at over $200. Having a complete-in-box version of this variant is worth much more, with auctions online pricing the game from $350 to $650.

3 The Space Adventure

An epic tale in space

One of the last games to be published for the Sega CD was The Space Adventure in 1995. The game was originally released in Japan for the PC Engine in 1991, but was later made available in North America and Europe. While the game is known simply as The Space Adventure for its second release, it's actually a sequel to a PC-Engine game in Japan called Cobra: Kokuryuuou no Densetsu from 1989. Both titles are based on a manga/anime series in Japan called Cobra, a futuristic tale about a man escaping his past from enemies that seek revenge on him. The plot of the game is based on one of the earlier adventures from the manga series, and is widely known as one of the first games based on a licensed anime to receive a mature rating.

While receiving criticism for various elements during gameplay, The Space Adventure was also praised for its gameplay style, which was similar to that of the game Snatcher, also available on the Sega CD. Many critics disliked some of the poor animations and lack of voice-over, leading to poor reviews in various outlets. Today, the game is a collectible that could be valuable to Sega collectors. Loose copies of The Space Adventure are worth about $230, while complete copies of the game are valued at over $600. Some online auctions have sold the game for as high as $1,100 at the time of sale.

2 Snatcher

A robotic future

Speaking of Snatcher, this is also a valuable Sega CD game that collectors love to grab. It's credited as one of the earlier titles written and designed by legendary designer Hideo Kojima, following his work on the original Metal Gear for the MS-X console. Snatcher was released in 1988 for the MSX2 in Japan, and is an adventure game with a heavy emphasis on story. Gameplay is done through menus that enable players to explore locations and discover information crucial to the plot, which can involve speaking with various characters and interacting with objects and items.

The plot of the game involves a dismal future in the aftermath of a biological weapon wiping out the majority of the human population. A man named Gillian, who suffers from amnesia, works for a group called JUNKER to hunt down humanoid robots called Snatchers that kill and replace humans in society. Somehow, Gillian's past is related to the Snatchers, so he pursues them with hopes that they will give him the answers he seeks. Many people enjoyed the overall story of Snatcher, which was praised for its maturity and uniqueness compared to other games released around that time. Snatcher is a valuable game for collectors, either loose or complete in box. A loose copy of Snatcher is worth over $400 alone, while a complete copy can be sold for over $1,200, and even higher in some auctions online.

1 Keio Flying Squadron

A shooter gem

Keio Flying Squadron is a shooter game for the Sega CD that was originally released in Japan in 1993. It later came to North America in 1995 and was received well by critics. However, the game did not do well commercially in either territory and remained an obscure title for a long time, garnering a cult following years after its initial release on the platform. The game takes place during the Keio era of Japanese history, focusing on a young girl named Rami who must recover a stolen artifact, the Key to the Sacred Treasure. Riding her pet dragon, Rami battles legions of enemies as she ventures forth to recover the key and return it to its rightful place.

The gameplay of Keio Flying Squadron is like other side-scrolling shooters of the era, with tons of enemies appearing on-screen to be shot down. Picking up power-ups can boost Rami's shots and offer assistance in tough moments against enemies. The game has animated cutscenes and an overall comedic tone that is reminiscent of different anime comedy shows, with Japanese pop culture and folklore references. Much of the game's characters and design are inspired by the Japanese folktale Kachi-kachi Yama, which is about a rabbit and a mischievous tanuki. Keio Flying Squadron is one of the most expensive Sega CD games you can find, with loose copies of it going for over $800 online. Complete-in-box copies of the game are much more valuable, with some auctions selling the game for anywhere from $2,600 to $2,700.

Rare treasures of the Sega CD

Despite being an accessory to boost the relevance of the Sega Genesis for longer, the games for the Sega CD were interesting experiences. Although not every game on the platform was a hit, most of them were able to find a cult following years after their release. Retro collectors who love Sega titles are always looking for rare Sega CD games that are valuable. But while some can find the beloved hits of the console occasionally, you might not be able to get your hands on these incredibly rare and valuable games.