Basically what Aki-at said. I don't mind getting a new label on the forum, I've said many times I'm not a fan of Sega as they are now. I used to be a fan of Sega, and I am a fan of some of their development teams (AM2, Nagoshi's mob) and IPs (Virtua Fighter is still my favourite game for example) but overall? They may as well be EA or Activision for all they actually do good anymore.
Not to mention I stand by my comment, what has Capcom done recently that's worth getting excited about? Look at their fighting games, the only good ones to be released in recent years are re-releases and that's because they let Iron Galaxy do everything (original arcade graphics and settings, GGPO online) compared to Capcom's own efforts which are considered the worst fighting games on the market just about (SFIV being a game of option-selects and gimmicks, and Sleep Fighter X Tekken a nap being one of the poorest fighting games in memory). They've run Resident Evil into the toilet, RE6 being the single biggest dissapointment in gaming history for me. Dead Rising 3 looked horrible as well, although I haven't played it so I can't comment too much.
Sega itself, as Aki said, isn't too bad on quality (although, Sonic Boom?), but their release schedule is so sparse it's pathetic.
EDIT: In response to everyone's dream crossover fighting game from the two, which would be the sweetest peach to come from this possibility, who would actually handle it? Capcom's fighting games have fallen a lot recently, the best we could hope for is probably Marvel vs Capcom 3 tier, which I could live with, but it's still a horrendously broken game.
Sega could try to implement it, but unless it's AM2 taking on developing duties, I worry how it would turn out. More likely they would outsource it to Sumo or something and we'd get Sonic & Buddies vs Street Fighter and it'll be a line for line ripoff of Smash Brothers with 12 Sonic Characters, Pai from VF and one of the characters from Gain Ground because "We know what the hardcore fans of Sega's fighting games wanted from a Sega fighter *winks*"