I really do hope that this comeback is to be seen in the future not as a failure to return to his former heights but of a success showing that he was able to match the best drivers in the world because that's precisely what it was.
If we're candid we have to agree that Mercedes is to blame, Brawn is to blame, the whole team is a fancy name on top of a better-than-average HRT or Marussia, a sad joke, really. So MSC leaving Mercedes makes perfect sense.
Also, F1 is less interesting without Schumacher in it. It's also less interesting than it was years ago before the FIA started banning every new wrinkle, put bad tires on the cars to "make races more interesting" (and less like races -- couldn't we look up the definition of "race" and be astonished again?).
Now, I don't think he's the best pilot these days, but we'll never know how good he was in his comeback because he never had a car nearly as good as he is. And anyway, he's plenty good, and especially when he has a good car under him. How great would Vettel be without the RBR? Hamilton w/o the McLaren? Button, a career 2nd driver, is pretty damn good at McLaren, when everyone thought he was a one-shot with the (lucky) Brawn. Give Michael that car and he'd be in the hunt for the title this year. Yeah, he's screwed up a number of times, but my guess is he just got tired of riding a bad horse every couple of weeks.
What I still don't get is why MSC didn't take up with Sauber, and nothing I've read makes any sense, except, of course, that he was genuinely tired of messing with F1. He knows Mercedes is going nowhere, after the mess they've made of the last three years. He knows Sauber is the better, faster, more tire-friendly car, readily able to mix it up with the top tier (not saying it IS top tier, just that it's close enough to podium a few times).
Most important is that Schumacher's departure is F1's loss. We've got good and interesting drivers in the younger crowd, but nobody that holds a candle to Michael in the star department. Kimi is sort of similar--a magical driver maybe a bit past his prime but still quick. Yes, people have to retire, but Schumacher showed this year (and some of last year) that he has caught up and need not be embarrassed by his performance. He lacked only a ride of consequence. And got instead the ridiculous weekly excuses from Mercedes, the assertions that they were "continuing to push," and "bringing new parts" to the next race, all the while sliding, sliding down behind the lesser teams. There's something infectious and exhilarating about seeing Michael in the pits, Michael chatting people up, Michael in the car. Yeah, it's hero-worship of a kind, but it's also something about the history of the sport, the remarkable career still active, the smile, the chin.
If he has any desire to drive he should have signed on with Sauber for a last hurrah, beat Mercedes soundly next year, taken a few podiums and maybe a win (or two) before closing the book. Last week he drove from 23rd to 11th and could go no further. The only thing holding him back was clearly, obviously, the car.
Me, I vote he changes his mind.