I saw Thor and it Totally Rocked. I've never read any Thor comics, and I don't know anything about The Avengers - but this movie had some moments of pure gold. It wasn't all good, and it wasn't all kick ass, which I liked.
I'm not going to review Thor because there are plenty of others who've already done that, but Kenneth Branagh brings just enough cred to the party to make it an interesting, sometimes thoughtful, and totally fun experience.
The fact that the lead is an Aussie also helped. But what I really liked were the three or four moments when I was totally taken into the story, immersed in the awesome visual spectacle -- which unlike some other CGI extravaganzas -- really, really, worked. I don't expect these moments in movies anymore, I just appreciate them as they come along, and in Thor they came along regularly.
The way I look at movies these days is, don't go with big expectations and you'll usually be pleasantly surprised. Thor surprised me, and awed me a little bit too.