I know I'm rather late, but I just saw it, so there.
I think that does play a major part. I really didn't want to like this movie as much as I did, I didn't want to justify the reboot. But Spider-man's portrayal is, obviously, so important to the film as a whole that the improvement I saw in Garfield (and I didn't hate Maguire) made me like it. Garfield's version just fits Spidey better, his awkwardness felt very real as opposed to Maguire's weird awkwardness. Replacing Kirsten Dunst also did not hurt at all.I think one's enjoyment of the movie hinges on whether you liked Garfield's version of Parker/Spider-man better than Maguire's.