I think Infinity War is the best, but Endgame will be remembered most fondly over time for representing all of them and sticking the landing. No Way Home, the bloom will come off the rose eventually and people will start to see the flaws/pandering. Iron Man 1, I never thought was that great at all, and gets grandfathered in as some masterpiece mainly out of nostalgia. When it came out people really regarded it as only marginally better than Ghost Rider but not on the level of the Spidey or X-Men movies; it's okay, has a ton of third act problems, it's mostly given too much credit for starting the whole thing. That summer it was completely overshadowed in terms of hype and reception by The Dark Knight, it's revisionism that this has flipped now to people thinking it was some game changer out of the gate. If there was no MCU, after Iron Man 2 it would probably be forgotten in the way the Fantastic Four films are now.