that's great

I really hope that it does manage to become the best selling metroid game. I loved it, and wish I could have played the earlier games using the same control style. the only complaint I had about it was no quick ways to pull a 180 turn, but nearly every FPS suffers from that.
I loved the controls, the mood, the little substories that you got from the archeology and the way you gained information about enemies by locking onto them was a stroke of brilliance, as it was like having a constant subtle strategy guide through the whole game.

Really good!

I haven't bought it yet.
I loved Metroid Prime, but the endless backtracking and open world was sometimes a little too much for me, so I skipped Prime 2 (and with me a lot of people did that, considering the sales gap between 1 and 2.

But given the good reviews I might give Corruption a try. Do I miss much story from not playing 2?

If you don't play prime 2 before corruption at least read the scans online, and watch the cutscenes , because you would be somewhat lost. Now if you want some more pursuading to buy the game here is a fanmade trailer that I found on youtube. It was the best one I could find.

It should pass super metroid eventually, and could even get to about 1.7 mill with some sort of Platinum release in the future.

well it passed 1 million 2 weeks after cmas, and has sold about 300k in 3.5 months, I see it selling 200k in the next 3 months, then 100k, then 250k(holiday 90 day period) so that would take it to about 1.7-1.8 by year end, 2 million lifetime is possible.

You should definitely give Corruption a try, it's awesome! :) It kept all the good things from the first Prime, improved upon them, removed the bad bits and made the whole thing better. The controls alone make this my favourite Metroid game ever. 

Also, you don't really miss much if you haven't played Echoes. I didn't, and I got through Corruption absolutely fine and understood everything about the story. All you really need to know about the story from Echoes is that Dark Samus was there, Samus defeated her at the end, but she somehow survived. Corruption's story actually has more ties to the first Prime.   

I did the same as you for mostly the same reasons. I did pick up Metroid Prime 3 though and I must say I am extremely dissapointed. It has none of the charm the original had it seems. The controls feel much worse, and the worlds feel much less alive. The use of the motion controls are absolutely terrible save for the grappling hook which is kinda cool. Overall I must say the game is massively over-rated on this board. It is not a bad game, but really just plays like your standard mediocre FPS.

 Metroid Prime 3 controls>Metroid Prime and 2. The controls in prime were horrid. Lock On targeting was what kinda made the game not the best metroid game to me. Prime 3 controls I believe are the best on the wii to this date. It even rivals some computer games. I believe the reason why you think the worlds are less alive is , because you are getting used to the art direction. I think prime 3 is an overall better game , but that is your opinion. I just felt I had to tell you that I disagreed.

I love Prime and I love the controls in Prime 3. But I enjoyed Prime so much more cause it was completely new. By the time I played Prime, Prime 2 and Prime 3 I was rather bored of the whole backtracking, exploring experience. If not for the controls I don't think I would have enjoyed it at all.