Still a unique, and I think worthwhile, entry in the Virtua Fighter series. While the PS2 version is interlaced, and has no anti-aliasing, and looks super-jaggy and pixelated as a result, it has an AI mode where you can create and train your own AI characters--and even coach them through the game's single-player modes, or fight against them yourself (and they're separate, rather large files, so you can even trade them to your friends).
4 is, in fact, where Sega AM2 went all-out to make Virtua Fighter a great single-player experience. The menus are really cool, and even customizable--hit the D-pad left or right in the game options menu to change the wallpaper!--there's a super-extensive training mode that does a good job of teaching you the many, many intricate moves for each character--and other menus even track which moves your AIs haven't learned yet--and the game introduced what would, in the follow-up, Virtua Fighter 4: Evolution, be known as "Quest Mode," but here, in its pure form, is simply called "Kumite."
Kumite pits your customizable player character--you gain wearable swag from winning fights--against what feels like a limitless number of named, customized, maybe slightly behaviorly variant AI characters, each with their own rank and skill level; beat enough of them at your own or higher ranks, and you gain a rank yourself. Win or lose, though, the game goes straight on to the next fight, so it really feels like an endless series of matches against a sea of different opponents, at around your own skill level. It's...basically exactly what I want to be doing in a fighting game.
Later VFs, starting with VF4:Evolution, rename Kumite and break "Quest Mode" up into separate bunches of virtual arcades, so you have to drop out of fights from time to time to go find a new locale with opponents better suited to your changed skill level. Those games also add more variety to the action in terms of occasional tournaments and things to play through, but they lose the ultimate immersion of VF4's uninterrupted Kumite battles.
Back in the day, the fact that, if you lose too many fights in a row, you can lose rank, ended up intimidating me; if I went too long away from the game, I would feel I had lost a bit of the skill level I'd built up, and so I would be likely to lose a rank if I tried jumping back in. In the end, I mostly would just throw an AI character of mine into Kumite and leave the game running, checking in on them from time to time--best "screen-saver" ever. : )
VF4 does not force you to have the lightbulb-style hit flash FX light up the characters when they strike each other: it's an option you can leave off--later VFs, including VF4:Evo do not let you turn the flashes off. I'm prone to photosensitivity, so I appreciate 4 giving you the option!
If, like me, you don't really like the side-step evade/dodge mechanic introduced to the series in VF3 (at least here it isn't on a separate, fourth button like it was in 3), you can even train an AI and not teach them side-stepping, so you can then go fight them for dodge-free battles. This did, however, prove chancy: the first AI I taught, a Lei-Fei, seems to be almost 100% evade-free; the second, though, a Wolf, evades like mad; I didn't teach it to him, so either AIs naturally come with some minimal evade knowledge--and they definitely self-reinforce knowledge of a move the more they succeed in using it--or he learned it from an AI during the overnight Kumite session I put him through for necessary skill and rank improvement. And unfortunately, while you can tell an AI not to use a certain attack if you catch them using it, evades/dodges do not seem to be moves the AI will understand you to be discouraging, so, once they know to evade, nothing can stop them from trying it again. : P Ah well.
VF4, with the hit flash turned off, is nice and non-flashy except for two things: there's a crumbling Roman ruins stage with lightning flashes lighting up the sky--reminiscent of Sarah's stage in VF2--and a white screen flash just before each fight actually begins.
If I'm sticking to Kumite I can just quit out if I hit the lightning stage randomly, so that's all right; the white pre-fight flash is more annoying--it's gone in 4:Evo, although there of course you can't turn of the hit flash FX...--but if I remember, I can just keep my eyes closed until the announcer actually calls the fight to begin. : P