I liked Avengers a bit more, not 10/10 my favorite movie ever, but I did enjoy it a lot. Aside from the awesome, but totally impossible in real life helicarrier, most of the rest of it more or less made a certain kind of sense within the powers they were given. The characters were great, there's a number of lines and interactions between the characters that are really enjoyable.
For Pacific Rim I liked the nerd characters, but that's about it.
If you're going to make giant robots, make them look like beastly death machines, don't just make a standard human frame with fists. (AKA, make it something more like the walkers in Star-Wars or District 9, or Mech Warrior) I'm biased against human frame robots. I didn't like most of the bots in transformers either.
Use the damn sword from the beginning! Mechs doing wrestling is just weird to me. If they'd actually made more use of giant swords and agile robots that could put on some entertaining swordplay that would have been a lot better. As it is only the last two fights feature it in any great detail and I didn't think it was that impressive of a battle.
A nuclear powered robot is still electrical.
Why does every fight scene seem to take place in the ocean, yet somehow the bots are only knee deep in water?
Why do they "train" with staff weapons, when the robots don't even use staff weapons. You know, if one of the robots actually had been using a staff weapon then it would have been a lot cooler.
...And a myriad of other things like that that add up to a "this is nonsensical, and it would have been more awesome if they had spent the time to make it a bit more logical" conclusion in my book.
The main characters are bland. The characters in Avengers have a lot of flavor, the characters in Pacific Rim, not so much. Except for the nerds, they were awesome, but they weren't the main focus of the show and didn't get all that much screen time.
I suppose it's just weird to me because I haven't watched many Kaiju / Humanoid Robot shows. I've never had a deep affection for that stuff.