The reason why its so good is because its easy to pick up unlike the clusterf**ks that are fighting games today. It doesn't take 2 hours to learn a person's moves and the combos are simple enough to do without being a pro who's played the game for like 2-3+ years. The fighters are far from identical. The only ones that are close to being identical are the Shotos (Ryu, Ken, Akuma, Sakura, Dan, Sean.) but in the end, even they all are different. And did you say you enjoyed DG: Final Bout more? If I may borrow this phrase for a bit: That is the biggest load of bollocks I have ever heard.
People shouldn't be tired of this game, because I would be surprised if a single person lays a finger on that atrocious piece of trash. Less characters and More combos does not equal better. Everyone has a different taste and everyone's tastes change. They want more variety NOT less. So having that many characters means there is a possibility more people would be satisfied.