X-Men: Children of the Atom is an easy game to take for granted, given the seeming hundreds of Capcom "Versus" games that have since came out with this graphical style and these characters playable. Back in 1994, however, this was a pretty big graphical jump and introduced a lot of new gameplay twists to the standard 2D fighting game template. It also outdoes some of the games that followed it in a few respects.
The roster is broken up nearly evenly, with five reps from the X-Men squaring off against four Evil Jerks. On the Jerks side you get Omega Red, Spiral, Sentinel and the Silver Samurai, while the forces of niceness are repped by Wolverine, Psylocke, Colossus, Cyclops, Iceman and Storm. In single player mode this doesn't stop the sides from fighting their own people, however, as you get a random assortment on the way to the final boss.
The focus here is much more on combos than in the preceding Street Fighter games, but the game is really more about blocking, dodging and timing strong hits well. The game really doesn't play like Street Fighter, King of Fighters or anything that came before it, and it doesn't quite feel like anything that came after it in the Versus series either. If you picture, say, Marvel Super Heroes or the games immediately following it minus the Street Fighter-esque influence of characters like Spider-Man, you have a pretty good idea of how this one works. It's a totally non-watered-down version of the unique aspects of the Marvel games, undiluted by any Street Fighter influence. Really, what it's most like is the Darkstalkers series, with characters having their own idiosyncratic move sets you have to learn to get anywhere.
The game is also more brutal than anything else in the Versus series, at least in terms of computer difficulty. The computer comes at you like a cranked-up SNK game and gives you little time to adjust. The gameplay incorporates a few things that wouldn't really be used that much later in the series, however; for example, playing possum is a major strategic move here, as you can continue to lay down after a big hit for quite some time. A foe can hit you out of this with a low sweep or something along those lines, but it's a great way to dodge projectiles or a combo and then suddenly roll behind them for your own powerful counter.
The game takes more effort than usual to learn as it just has such an idiosyncratic style - common tactics from Street Fighter and KOF like jump-ins and rushdowns just totally do not work here. If you invest the effort, though, you're rewarded with graphics that were an amazing jump forward for 1994 and are still colorful and fluid enough to hold up today, great animated backgrounds that switch up depending on who wins the matches, a really good soundtrack by whoever it was that did Mega Man X's music, and generally very solid fighting action for one or two players that incorporates big jumps and big combos without turning into a cheesy button-mashing power-move spam fest. Some of these characters didn't make a re-emergence until much later into the Versus games, as well.
* Gameplay Video