Unlockables is the way to go for a fighting game. At least if it wants to have any single player value. The moment you have everything unlocked and available there is almost NO incentive to play the game. Even if it's just unlocking alternate costumes or character endings or whatever. There needs to be unlockables, or different storylines for characters or something, otherwise you have nothing to keep track of your progress.
Take the latest MK for example, Armageddon or whatever. Pretty much EVERYTHING is available right at the start, and while that's cool, it's also a big 'ol "So.... what now?" I mean, there weren't even varying endings for different characters if I remember right. You beat the game with one character, you beat the game with them all.
More people play fighting games for the multiplayer though. It's annoying when your bring your friends over for a brand new game only to find out you have to spend several hours on the game yourself unlocking everybody.
Exactly. Consider that we're talking about us arcade players here. If you want single-player stuff, make it bonus endings or colors or some shit. If it includes CHARACTERS, I get pissed off and usually stop playing. The DoA series blacktually did it okay, with most of the unlockable stuff being costumes rather than players. If half the fucking roster is "locked" then it's nonsense I won't bother wasting my time with. If I have to do busywork to get an experience that felt more complete in the early '90s, you're doing it wrong. Hell, I play KoF and some of the Samurai Shodown games religiously, and they have tons of characters. Same with MK Trilogy, Capcom vs SNK, etc. I remember being furious with Marvel vs Capcom games and the later MK games for making me "unlock" real, concrete features. I care about playing against a human, not a moronic computer. And if that experience is incomplete vs a more complete experience, I will gravitate towards the complete side every single time. Every single time. DO YOU HEAR THAT, DEVELOPERS? I DON'T MEAN 99 PERCENT HERE.
If you want to make it something like "ability to play with a certain type of weapon," fine. Do that. Maybe one-button super moves, or invincibility, or infinite gauge vs the computer, or artwork, or trivia, or designer commentary. But I want to be able to jump right in and play with most of the cool features and characters and stages immediately.