The earlier of the two games is the more traditional and probably better installment. It features the series' signature three-on-three bouts, where you keep playing as one character until he or she is knocked out. Beat up all three of your opponent's characters one after another, and you win. Traditional one-on-one battles can also be fought if you prefer, though there aren't many extra modes or other frills here--just plenty of rock-solid fighting gameplay, which you can enjoy either in contest with a competent computer opponent or against a friend. About four dozen different fighters fill out the roster, including many longtime SNK favorites, some of whom had been put out to pasture for several years before making their triumphant return in 2002. With 40-plus fighters to choose from, you can be assured that there's a fighter or three for everyone here. Yet SNK's unconventional character designs really shine through, resulting in a cast of characters that's genuinely diverse and not just plentiful. The gameplay itself is the epitome of 2D fighting, and it provides you with access to plenty of special moves and supermoves as each of the game's many characters. You can use these moves together with your normal punches and kicks to unleash devastating combos.
The King of Fighters 2003 is the more experimental game, though maybe that's a generous way of putting it. Still, it's the first King of Fighters game to introduce a fundamentally different play mechanic: a three-on-three tag-team system in which you can switch between your different fighters on the fly. This results in some especially fast-paced battles that play out like one big, hectic round of combat instead of like the typical five-round match you got in earlier King of Fighters games. At any rate, the tag-team mechanic is novel, at least in the context of this series. But the trade-off is that King of Fighters 2003 has a noticeably smaller roster of characters than 2002, and for some reason, the action itself feels a bit hollower. So maybe "experimental" is the right way to describe it after all. The King of Fighters 2003 can be a fun fighting game, and it's nice to know that the NeoGeo (and your Xbox, in turn) is capable of pulling off these kinds of multicharacter battles amid some modestly detailed pseudo-3D backdrops. But chances are you'll want to play more 2002 after a stretch of playing 2003. Again, though, it's 2003 that plays better online.
The King of Fighters 2002 is probably the better of the two games, but it's fun to switch back and forth between them just to compare and contrast.
Getting both games in a single package is definitely a treat, since being able to freely switch from one to the other somehow enriches the experience of playing each in turn. That's good, because when considered individually, these are some really bare-bones games, at least by today's standards. They've got plenty of content where it counts, since each game packs plenty of different fighters for you to mess around with. But don't expect much in the way of fancy presentation. These look and sound like old arcade games. At least King of Fighters 2003 offers a CD-quality soundtrack in addition to the original arcade tunes, though for whatever reason, 2002 does not. Both games feature plenty of speech from all the different characters, as well as some pretty good sound effects, but the synthesized music in 2002 mostly just drones on painfully in the background. Yet even though these games don't seem like much to look at or listen to, they definitely have their charm. Most of the characters are lovingly animated and are really fun to watch, as long as you can get past the fact that these games are running on some decidedly old-fashioned technology.
It's hard to get too bent out of shape about the weak points of this package, considering all that you do get in The King of Fighters 02/03. This isn't exactly the product that's going to make a fighting game fan out of anybody who wouldn't already fit that description. But if you've ever enjoyed the King of Fighters series over the years--or any of SNK's other great fighting games, for that matter--then you might as well spring for The King of Fighters 02/03. These games may be about as homely as anything on the market right now, but NeoGeo fans kept buying them, and others like them, for hundreds of dollars a pop year after year for very good reason.