I wouldn't say "great".."okay" is better for that. But I respect that your a fan and I'm sure you like it.
But it really can't compete with other games on the market, and it hasn't since it first released. The Cluster bonk of new character's they're always throwing in. The insane plots that try to be epic but mostly fall on mediocre. The new schemes they always seem to fall upon that make no sense
whatsoever. The music can be a bit repetitive if not horrible (Some songs are good though I won't lie). They always try to add new thing's to there game like "Oh this time Sonic's a werewolve!" or "Oh Sonic meets himself from the past uguuu!", those are just really dumb. And the biggest thing I can't stand about those games is whenever they try to cop out and go back to the original theme they always seem to screw that up as well.
Other then those small thing's I have against the game it's fun(ish). It's kinda like Duke Nukem, were waiting forever for a good game and the only people impressed by what's going on with Sonic is the fan boys. I used to be one and supported SOnic 110%, that is untill Shadow the Hedgehog came out.
But as I said before, your a fan and you like it so I don't blame you.
That said I really like SOnic on Dreamcast. Almost more then Mario 64...Almost
I respect your opinion as well. I understand where you come from...just let me say this:
Sorry but i think Sonic competed and he still competes with many games on the market. I'm not talking about CoD, Gears, etc.(just an example) but it's a series that sells over 2 millions with each game. Look at Sonic Colours. It sold over 2 and a half millions only on Nintendo. Sonic Unleashed sold over 3 and a half millions on all consoles. These are good sales in my opinion and many games don't see these numbers.
About the game plot i will agree that sometimes they try too hard. That's why many love Sonic Colours plot. It's simple, easy going and fun.
Music really depends on a person's taste. You can say that for example City Escape is the best song ever but if i don't like it then i don't so...it really depends.
Sonic's gimmicks. I won't lie that i didn't like the werehog but i have to say that it's an okay gameplay. Of course i prefer Sonic gameplay. About Sonic meeting himself in Sonic Generations, you shouldn't shoot down the plot before even knowing how it will unfold. Personally i find it a nice idea and i think it will play out very well.
I think the only mediocre/bad games Sonic had from Sonic Adventure 2 to Sonic Generations is Shadow the hedgehog(not featuring Sonic) Sonic 06 and Sonic and the Black Knight. Also to show you that i'm not blind i will put here Sonic unleashed's 40% of the game because of the Werehog.
Other than that Sonic games were successful in my opinion.