Avengers: Age of Ultron.
Well, not as good as 'The Avengers' or 'Iron Man' or 'Captain America:the Winter Soldier' but better than CA:The First Avenger, The Incredible Hulk, Thor: the Dark World and definitely better than IM3. (Not sure yet where I fit Thor and Guardians of the Galaxy into this.)
Spader's voice work is brilliant and the cast are, as usual, an excellent ensemble. May I also say a word for the superb animation of Ultron.
On the other hand, there is an awful lot of repeat of beats in 'The Avengers' and the script fails to match the wit of the first movie. Most of all though, there are too many damn characters. (I notice that 'Iron Patriot' has reverted to 'War Machine' and there are one or two other little things that suggest Whedon is not particularly happy with IM3.) Couple of interesting nods to fanfic fandom as well. The FX work was, well, patchy. The action sequences didn't show enough imagination, and some of the cutting was not good.
So, well worth watching, but non-comics fans may need a scorecard.