Sakura Taisen is not some obscure franchise and why would it's titular character be considered obscure? Using that logic, we should have Sonic, Virtua Fighter, Bayonetta, Yakuza, Valkyria Chronicles, Phantasy Star, Monkey Ball, Rise of Nightmares, Alpha Protocol etc before we even touched anything from Skies of Arcadia OR Jet Set Radio since the franchises I named have had better sales than either of those games. But if we want to talk about what best represent SEGA, then I completely agree with people who do not want Gum to appear in the game, at least as a playable character.
And what is wrong with complaining? Who knows where the Sonic franchise would be if people did not complain and/or voted with their wallets. Sonic Colours and Generations, solely Sonic games, only came about due to fan backlash and dismal sales for Silver, Unleashed, Black Knight and other major Sonic flops in the period before them.