Feels like I'm totally being ignored, but I'll say it anyway:
Where's my Sega All-Stars fighting game, you cowards? We've had tennis, racing and even a minigame collection, but the closest thing to a fighting game is that Dengeki Bunko game which Sega backgrounds (+Akira and Selveria in later versions).
I guess there was Fighters Megamix, but even that was pretty much just Virtua Fighter x Fighting Vipers with a few exceptions. And even then, it's only one game, from like 25 years ago. Goddammit Sega, you have such a rich IP library, rivaling Nintendo and Capcom in potential, yet you refuse to use it. Just think of the potential, like for example:
Eggman vs Arle
Sketch Turner vs Sakura
Sonic vs Alex Kidd
Bonanza Bros. vs Joker (if we're including Atlus property)
And hell, it's a surefire way to make your more obscure IPs more well known to a broader audience. I mean, it worked for Marth and Roy in Melee.
I'd also take Person 5 Arena as a consolation prize, even if the chances of a playable Futaba are next to none.