Raidou kicks Sagat's ass, in my opinion.
Bankotsu would kill Gill in the long run, and seeing as Gill can resurrect only once a day, he wouldn't be resurrecting any time soon after his death. Unlike Gill, Bankotsu can travel through dimensions, bring chaos and ultimate disaster to the world, fly and create powerful tornadoes. Gill I've heard can split a sea, resurrect, rain fire and ice meteors which seem smaller than average human beings, and split the sky...
Genra has Akuma beat. With a double-ended energy sword, village busting fireballs that take only a few seconds to create, as well as energy projectiles and shockwave attacks, he would kill Akuma, in my opinion. Nonetheless I believe this would be close.
I'd never put my money on Bison against Alpha-152. I've yet to see Bison do something impressive without a practically unusable plot device in versus matches as what I've seen of Alpha-152, who has, caused some if not most of the desctruction of DOATEC's tritower complex with shockaves, which have also disabled Hayate easily and nearly knocked out Lei Fang. Also Alpha's speed dwarf's Bison's as well as the fact it can teleport, not to mention that as of this point NOTHING has damaged or fazed it in the least...
Although this isn't a one-on-one kind of match, I gave my opinion of who'd win in those fights, since it's somewhat hard to discuss which team would win if everyone was fighting each other at the same time. As for who'd win the team battle I'd go with DOA.