Blazing Saddles, History Part 1 and Young Frankenstein are three of the best comedies ever put on film, and I'll fight you if you say an unkind word about any of them (except for the last 10 minutes of Saddles, I can't defend that). I even would support your opinion if you wanted to add Spaceballs to that last, though I'd rank it for lower.
After that, his filmography suffers. His Robin Hood was mediocre, and his Dracula was downright awful. Mel's style had been outdated, and it was right that he retire from filmmaking.
History Part 2 is a bad idea. Given his age (he's 95 years old), I doubt that he has a lot of input in it, despite his writing and producing credits. Either the writers will ape his style, which will fall flat with viewers, or they'll make something completely different from a Mel Brooks product and if that's the case, why bother? It's likely to fail either way, which will sully his reputation.
The only positive outcome is that a new generation of movie goers will be exposed to this legendary comedies.
