I dunno, I found the Mile High Club and 100%'d it and thought it was weak. At first it was "woah, this is awesome!" but that lasted for about 20 seconds until I'd walked all around and found that there was absolutely nothing to do besides randomly kill innocent people if I wanted and steal a plane. Which is pretty much like every location in the game except usually in those you also get to explode the same propane tanks, gas stations, generators as well. This game is all about "woah, look what I found!! This game is cool!" and then "oh, wait, there's nothing new to do here...zzzz".
I just wish they put more effort into making areas unique and giving them things to do. You know what would make this game better? Wrpg elements that give all these places quest dialogues and unique sidequests like Fallout. Maybe that'd mean they'd have to cut down the number of locations from 300 to 50, but I'd rather have 50 fallout1 level settlements (aka, a few npc dialogues, 1 or 2 short unique quests) than repeat the same thing 300 times.
I mean when most of the game is just blowing stuff up (or really boring after a few times
find the hidden upgrade packages [way too many of them in each area]), having bad combat with non-existant AI, bad driving, and wonky physics doesn't do it any favors. Sandbox games like Crackdown work because the combat is fun, the driving is solid, and in that game the building scaling/platforming element was well done. JC1/2 is like a set of super shallow and below average gameplay types thrown together in an amazing world.
I've been trying to figure out why I liked JC1 so much, when it had all of these same problems. I thought JC1 was awesome and it was the first sandbox game that I liked enough that I actually completed it. I think it was because early gen games get a free pass because just going "omg, these incredible new experiences like nothing before

" adds a lot of fun. I mean I thought Kameo was a fantastic action platformer as well. JC1 also had the advantage of actually being something new. JC2 is undoubtedly the better game in every way, but having done 20-30 hours of this in JC1, it feels too familiar and repetitive from the start.