His art on Spidey was fantastic. Everything he did on ASM and SM was pure magic. He was one of the first artists to deviate from the standard Spidey look, and it worked. He really opened the doro for Larsen, Bagley, and the rest of the artists who came after him.
His stories,on the other hand, were really kind of silly. They lacked imagination, and they dumped Spidey in this totally different world. It didn't even feel liek Spidey. In ASM, he was fighting Dr. Doom, and the Tri-Sentinel, and Venom, but in Spider-Man, he was being manipulated by voodoo, then he was fighting Hobgoblin (who I don't think he even hit the entire 2 issues) then he managed to not fiht anyone in the whole "Perceptions" arc, and then he hit Morbius twice in issues 13-14. He managed to do nothing to the Juggernaut in issue 16 aside frm web his eyeholes. The stories pretty much just featured Spidey posing in trees and swinging on buildings and looking cool for fifteen issues. That's about it. With McFarlane's art, that was okay, but it was jsut an empty read.
Yeah, not everyone likes his artwork, and some people say he sucks nowadays, but let me print a bible-truth right now:
If Todd McFarlane did a Spider-man book next week, which featured nothing but Peter in his classic red & blues, swinging around New York fighting third-rate muggers and talking to himself, everyone of us would buy it up so fast it would make the clerks' heads spin. Also, it would be about a million times better than the current take on Spidey.