They're not as mindshattering as MP1's boss fights but they're so polished and so fun.
The fights with Meta Ridley right at the start while in Morph Ball mode and while falling down the generator hole were super-fun. Not the deepest thing but it doesn't have to be. The fight with Rundas was also amazing, though I think that was mainly the work of the music (holy crap!), the plot and hypermode. Funny thing is I wasn't even all that invested in the other hunters, but just having that little bit of knowing where he came from went a long way.
**NOTE: THIS IS THE FARTHEST I'VE GOTTEN SO PLEASE DO NOT SPOIL**
I loved how deep the bosses in MP1 were, and I kind of liked the gimmicky nature of the boss fights in 2 though as I understand it a lot of people didn't.
These don't really seem to be that way so far. More like you just stop thinking so much and enjoy the pretties, and that's totally cool.
When I started this game I went "what's all this dialog and characters stuff doing in my Metroid Prime" but no it totally works once you get used to it. I am loving this game so far. :)
Ok not so fond of the big stompy robot guy you have to kill at the end of Bryyo. It's like a 30 minute fight just because he spends like 90% of his time totally invincible and 9% wiggling more quickly than a shot can go from your buster to his red spots. Some day video game developers will realize a boss that is invincible 90% of the time is never fun. Or at least I hope they will.
Ghor was kind of a letdown. The fight was fun enough but not much of a challenge, and the amazing tune you fought Rundas to had me overhyped for it. I beat him essentially without hypermode, except the last few blows have to be phazon (I watched his health meter when I shot missiles at him; they definitely did no damage when his health was low).