Final rooster looks like;
Characters: Sonic, Tails, Knuckles, Dr Robotnik, Amy Rose, Big, Shadow, Amigo, AiAi, Billy Hatcher, Zobio and Zobiko, Bonanza Bros, ChuChu, Alex Kidd, Akira/Jacky, Opa Opa, Beat, Ulala, Ryo and BD Joe. NiGHTS has a cameo.
Tracks: 9 Sonic Heroes tracks, 3 Samba de Amigo tracks, 3 Billy Hatcher tracks, 3 Jet Set Radio/Future tracks, 3 The House of the Dead tracks and 3 Super Monkey Ball tracks.
Minigames: ?
Total franchises represented: 15 series
Next is based on which hardware the series first appeared on, not the characters or their design
Arcades: 6
Master System: 1
Mega Drive (Or 16 bit): 1
Saturn: 1
Dreamcast: 5
Billy Hatcher: 1
If you think of the Xbox360 version, then you have 16 series represented altogether. There could be more in the way of minigames, keep that in mind.
How does this compare to SEGA Superstar Tennis?
Characters: Sonic, Tails, Amy Rose, Robotnik, Shadow, Alex Kidd , Gilius Thunderhead, Beat, Gum, Ulala, Pudding, Amigo, NiGHTS, Reala, Aiai, MeeMee
Courts: 2 Sonic the Hedgehog, 1 Samba De Amigo, 1 The House of the Dead, 1 NiGHTS, 1 Monkey Ball, 1 Virtua Cop, 1 Afterburner, 1 Space Channel, 1 Jet Set Radio and 1 Outrun
Minigame specifc appearences: Puyo Puyo, Space Harrier and ChuChu Rocket
Total franchises represented: 14 series
Next is based on which hardware the series first appeared on, not the characters or their design
Arcades: 8
Master System: 1
Mega Drive (Or 16 bit): 2
Saturn: 1
Dreamcast: 2
Billy Hatcher:
There you go folks