Overall Infinity War is clearly the better movie. But lets not forget, that Joss made all of that work, introduced those characters and made us care about them as a group.
And the other anon is imho right, while Infinity War had awesome battle scenes inbetween (fight against Thanos, Thor entrance ), the group fights of Avengers 1 were setting a new standard and are on the level, if not better than those of Infinity War- with a comparably TINY budget.
That is what Joss Weedon did without someone else showing him a rough blueprint as to how to do it. He and his team did that 100%.