I liked Prime 3. There are a few problems with Prime 2.
1, and this is the worst one, the areas. They are all pretty bland with the exception of Sanctuary Fortress. They all have the same overtones of brown and more brown, and Dark Aether is even worse, with constant purple everywhere.
2, The musical themes for the different areas are somewhat dull with a few exceptions, (Torvus sounds like a Prime 1 overworld theme, and lower Torvus is a neat remix)
3, Dual World Gameplay. It's a nice concept, that the Leviathan split the world into two dimensions, but the way it's implemented is just so bad, and boring and it drags on forever. "Oh I have to go all the way over here to get to there, because convenient ingworms mean there is no passage that way" And don't get me started on the key hunting. HOOOLY SHIT, did they seriously think we wanted more of that? That shit was intolerable.
4, Ammo count. On a BEAM weapon. What, the fuck, is this. I don't even. Really? What was wrong with the way every other Metroid game did it? or the way Prime 1 did it? With doors and puzzles possibly requiring you to waste ammo, you are going to use an ammo count? WHY. The selection this time around was also pretty pitiful. Just the generic light, dark, and combination. And the Annihilator beam is really not even worth it, since it uses ammo from both the other weapons. Charging it, at least, is futile, since uncharged alone, it already deals massive damage and homes in on enemies. And the charge combos are not impressive. Annihilator's is neat, and Black Hole is interesting, but Annihilator's charge combo takes like 30 missiles and 30 ammo from both the light and Dark beams, making it hardly worth the effort when you can just use Super Missiles. And Sunburst was terrible.
5, too much emphasis on combat, it felt like.
6. I didn't really like that the game forces you to take damage in Dark Aether for pretty much 3/4ths of the game, with Samus' health tanking like a rock before the Dark Suit. And No, the fact that the safe points regenerate health does NOT make it better. I mean jeez, Even other M's forced No Varia Heat Area run is better than this, because yknow, it doesnt force you to go back and forth through the sector without the Varia Suit all the damn time. It's just one and that's it, any future heat runs are heatproofed. (unless, y,know, you jump in lava)
7. the Screw Attack controls like total ass, and I know you can't control the direction. No, the trigger for it after double jumping is so ridiculously specific that half the time it doesnt trigger at all because I tried it too early, or too late.
8, I just could not bring myself to give a shit about the Luminoth. The lore felt too disjointed at times, and I found myself more interested in their interactions with the Chozo.
TL;DR, it was bland and uninteresting, and introduced too much too fast. I mean, even Emperor Ing was not too impressive. Mainly because he looks like every other Ing out there. (and his hitbox on his core is so fucked up it;'s not even funny. I cant count how many times a shot SHOULD have connected, but it didnt.)
Prime 3, while more linear in structure and again, has a slight more emphasis on the shooting, still balances it out by having more diverse areas, (planets! You can travel to planets!)
The music I think, picks up a slight bit from 2,
The PED Suit is an interesting mechanic, although it tends to make the game easier as a result,
The Screw Attack controls well, and doesnt have such a ridiculous trigger timeframe.
I actually found it interesting to interact with the Federation, and Exploring the destroyed remains of the GFS Valhalla was one of the coolest parts. That felt like some Dead Space shit right there. That place was pretty creepy.
Skytown, Elysia, DEFINITELY felt (and sounded) Chozolike, And I liked how it was like, basically a Chozo Steampunk thing.
I finally gave a shit about the story and the lore, And how it connected back to the first two Primes.
MOTHER BRAINS.
MOTHER BRAINS, EVERYWHERE.
Dark Samus design got a cool upgrade.
AHHH IT'S THE SA-X! Oh wait, it's just Gandrayda mimicking you in your normal Powersuit and kicking your ass with it.
Also, Rundas. (R.I.P. :< )