Sadly, I'm not a fan of his either, although I will admit that he did much to revolutionize the genre; to actually make it fun, instead of as ponderous as La Ponderosa. His contribution is strictly aesthetic (as in bringing in Claudia Cardinale to the proceedings, certainly an improvement on the genre). Plus he is to blame for the stardom of El Clinto (Eastwood, to you), and he gave us some fantastic cowboy music from Ennio Morricone.
I find Leone's movies cheesy and cartoony and difficult to take seriously, although lots of film mavens adore them. Perhaps I just don't get it.
I'm the only person I know who h.a.t.e.s. Once Upon a Time in America, his gangster movie with Robert De Niro and James Woods.