- Just Cause 2 is too open in the sense that you can get a helicopter early on and take out everything from a safe distance. The game gives you other options for causing destruction but they're not really that efficient comparatively. It gets boring at this point because it's basically a "solved" game.
- My issue with Just Cause 2 speaks more to my issue about open-world games. You need some kind of constraints on /what/ you can do to force you to make interesting decisions. If you don't have those constraints, you'll quickly find a single perfect strategy and just go with that all the time.
I feel like Open World games are made for people who would put constraints on themselves. They're a sandbox, and while there can one easy way to make a sand castle, what's the point if you're just gonna do what's easy? That's the type of mentality that gets me to enjoy these kinds of games, at least. But I'm the guy who can't play Pokemon without a zillion self-made rules and objectives, because that's the only thing that keeps me invested, to the point where it's literally the only franchise I'll consistantly complete without a break.
It's more like JC2 kind of went overboard with it for my tastes. Same reason why I didn't like Saints Row 3 as much as 2, although I'm not sure WHAT constraints you could put on SR3 to make it... not have a completely uneven difficulty sinewave.
I think my bigger issue with JC2 is that the main advancement mechanic of causing chaos got pretty one note pretty fast because it just turned into "blow up whatever map objects are red," which meant that doing stuff on foot involved a lot of tedious and methodical searching, whereas helicopter was just strafe whatever and win. Although I've /never/ been the kind of person to get much enjoyment out of random acts of destruction in sandbox games -- I'll do it and it's fun for a few minutes, but making the entire metagame nothing BUT that*?
And then death didn't seem to have any major punishments other than sending you back to the previous checkpoint, so the whole aspect of /losing the heat/ felt pointless to, and that could've been an interesting scenario to play through.
(*Although I guess I'm an idiot for playing the GTA games/Morrowind normally and not just turning on all the cheats and ignoring the main game).
And apropos to what jawsh was saying about XBC, being open-world shouldn't mean the story's worse in a game than in a linear game. An open-world game that's story-focused and well made in that regard would have sidequests that expand the story/worldbuilding/characterization/etc. Xenoblade's sidequests not doing this at all is /noooot/ indicative of how sidequests usually play out in open-world RPGs.
Most sidequests-heavy WRPGs, especially modern ones, have a LOT of storytelling and worldbuilding content in the sidequests, and for a lot of people, the story is the draw there. I mean I don't even think you really get major loot/experience rewards for doing sidequests in WRPGs these days, experiencing the stories therein is like the only reason to do them.
In other words, someone who was drawn to Torment/Ultima/Fallout/The Witcher because of the storytelling and lore would probably /not/ find much merit in XBC for the exact reasons you mentioned.
Although, for a lot of reasons, I wouldn't even consider Xenoblade an open-world game. It was pretty much a bog standard linear JRPG that just had huge maps with very little to do in them.
It's sidequest were also reductionist enough that I'm not sure I'd even consider most of them sidequests. You're, what, just running around in circles grinding mobs/random map sparklies for loot? That's about as much a sidequest as walking around in circles to get in random encounters was in Phantasy Star 2. Or you just do them incidentally, which is actually how it plays out most of the time, in which case it's more like you're getting random experience boosts for not doing anything.
(Persona 3's sidequests tended towards the same kind of GRIND RANDOM ENEMIES FOR LOOT stuff, which is one of the things that killed my interest in that game).
JC2's problem for me is that it was too repetitive for its size, although that's quite possibly a premature assessment and I never fiddled with the difficulty settings.
XBC is more like an awkward approximation of an open-world game that got grafted onto a linear JRPG, didn't really get the open-world stuff right, and is nooooot indicative of open-world games in general.