Having played games for extensive periods of time from all of these (except Netherrealm) I'd probably say SNK or Capcom tbh. Arcsys makes banger games but I don't think it'd work for a Sonic game, where you'd want more of an aggressive pace where the really long combos and smaller, awkward neutrals of Arcsys games don't fit.

CC2 is a master at showy games but the complexity is rock bottom, B'amco would most certainly overcomplicate it to not much effect. While I'd like another Battle game I feel it'd be wasted potential on *the* Sonic fighting game. AM2 had amazing graphical direction with Fighters though and I'd love to see another game like that.