In all Metroid games, including the trilogy, Samus can don mulitple different suits giving her varying attributes and abilities. But one of the coolest parts about any Metroid game is the way the heroine looks while weraing the different suits. MP starting the beauty off with a very attractive looking Varia Suit. Complete with extra large shoulder pads and a shiny looking tan and yellow color scheme Samus was ready to go. She then lost her cool looking suit and got a gross looking thing. She later got a slick looking black and silver looking suit with some Phazon corners. MP3 also had some cool looking suits, well, at least sort of cool looking. None of the suits in MP3 were really all that crazy looking to be honest, mostly just the same ol' same ol' with a slowly darkening color scheme.
MP2 is where the real beauty comes shining through. Not only do the suits in MP2 look far more unique and original than the other two games, but without them it would be impossible to survive in about half of the MP2 universe. The suits in MP and MP3 are vital, yes, but not near as vital as the suits in MP2. Above you will see two images of the Light Suit, the most glorious looking suit in the Metroid series.
1) Metroid Prime 2: Echoes (Light Suit)
2) Metroid Prime (Phazon Suit - Unlockable Metroid Fusion suits)
2) Metroid Prime 3: Corruption
There's more to graphical comparisons than just pushing the limits of polygons and textures; the art design is also an important concept. When comparing the art direction of the three different games, there are a few things to mentions: impact and immersiveness. The art direction in MP was the game with the most impact on the series, you can tell that by the way MP2 and MP3 look. MP2 is a slight step up, but MP3 is the game that really polishes the art design with multiple planets and brings you into each world.
When it comes to pushing the graphical limits, I'm talking polygons here, MP and MP2 are no competition for MP3. In fact, the number of polygons are decently close to that of the other two games but the textures are double the resolution. So all around the game is sharper and more detailed. Not to mention the game runs in progressive scan, as does MP2, and widescreen.
1) Metroid Prime 3: Corruption
2) TIE - Metroid Prime 2: Echoes and Metroid Prime