Personally, none of the other Metroid Prime games have been anything like the original. I think they got it right with the original and it just spiraled downwards from there. Echoes was decent, but it was not my favorite at all. Some of the boss fights were a bit ridiculous, especially when having to redo large portions of the game again if you die against them, and the whole Sky Temple Key thing was much too hard and confusing, IMHO. MP2: Echoes also had some ridiculous items, such as that one underwater item you got deep down in the Hydro Drum thing where you had to go down to get another item once you got the Annihilation Beam.
They also made MP2 have way too much backtracking and finding....I do like a few of the items you get in that game, though :) The Screw Attack made me happy :) They also did some pretty ingenious things, IMHO.
Anyways, Prime had all of the elements right. It just felt like a Metroid game where as MP2 didn't. Metroid Prime also had some of the most memorable sequence breaks out of all of the Metroid series of games IMO. I especially loved getting Space Jump first, and then wreaking havoc and getting a whole bunch of other things early. Also, getting Plasma Beam early was also especially memorable.
Metroid Prime 2: Echoes didn't have very many good early items that were actually decently easy for the average game to pull off and had harder sequence breaking moves....I never could make the Roll Jump work :/
Prime and Echoes are really similar. Looking over both games, there really doesn't seem to be anything at all that Prime did much better than Echoes or Echoes did much better than Prime. There were some differences; Prime has more of the "classic" Metroid feel, while Echoes is just more polished in several other ways; Prime generally has its upgrades in one place at a time, Echoes makes it easier to get to the ones that aren't; Prime has easier sequence breaks, Echoes has better ones. I personally prefer the differences the way they are in Echoes overall, making it my favorite Metroid game and Prime a close second.
Corruption is another story. It's good, but nothing like Prime or Echoes in terms of most of the things that made them great, and just overall quality.
Prime generally has its upgrades in one place at a time, Echoes makes it easier to get to the ones that aren't
Bullshit. Power bombs are the dictionary definition of a pain in the ass to get.
Using the natural route, there's a short route through Great Temple back to Torvus, or to Agon to use the path from there to Torvus. More significantly, once you get the Power Bombs, you can just turn around and walk right back into Sanctuary. Compared to all the items in Phendrana, for which you have to go through the completely linear route through Magmoor both ways and sometimes getting forced to go some other way in the process, that one item seems rather tame.
mp2's biggest crime is having the next item way too far away from the last, especially PBs. in mp1, that isn't as apparent since mp1 feels smaller. sequence breaks enhance mp2 a lot just for the amount of backtracking and time cut.
btw, ILS is the coolest trick in any of the primes, beating SJF. too bad it was discovered way too late.
I also agree with TheOthin that the items in Prime 2 were just spaced so far apart, and even the Sky Temple Keys...my god...making us have to go all the way back down into the Crypt part of the map in that one area just to use the annihilation beam on that one door? Ridiculous. There were some that were fairly close together, but most of them were just so far apart....
In fact, it's the exact opposite of what I said. By endgame, you have two ways to get directly from any one area to another, and even more ways to go through another area, so getting where you need to go immediately couldn't be easier. From the moment you get the Power Bombs, and even more so when you get the Light Suit, there isn't much space between any two locations on the map at all.