I personally prefer the more gritty realistic universe of the Nolan Batman films. Whilst I didn't mind, in fact quite liked, the first Avengers, I thought the second was borderline awful.
I'm a massive fan of Spader and thought he voiced Ultron brilliantly, although they played up to this with at least one too many monologues. That said I found Ultron to be far from a good antagonist, bordering on comic relief, his "not again" line after being foiled and pummeled for the Nth time summed it up for me. The first film genuinely made me laugh on a few occasions but found the gags in the 2nd to be way to contrived and don't even get me started on Quicksilver's Russian accent.
Reading through this again I may just be being a miserable git.