I am so pumped for Metroid Prime 3, and I'm sure it'll be the must have hit for Revolutions launch.  Oh, speaking of launches, the 360 didn't have any killer-aps to start off with, while Nintendo will likely have Mario 128, Metroid 3, and Smash Bros. at launch - all of which will be must haves.  Anywho, where was I?  Ah yes, Metroid, here's why I think it'll be sweet:

1-Metroid Prime 1 and 2 looked so much better on the GameCube than most GC games partly due to the fact that they had a very fast, efficient, game engine which took advantage of the system quite nicely, rendering beautiful environments and having a rock solid framerate to boot.  Now here's the kicker - Rev's architecture is identical to the GC's, so Retro Studios won't have to build a whole new engine designed for Rev., they can simply continue optimising what they have, plus take advantage of the newfound power in Rev.  Sometimes when optimising, developers work on "hotspots" in their code which get used alot, and go down to assemby language to optimise that one chunk of code extremely well.  Now, assembly language is intimately connected with the cpu, but since Broadway has the same architecture as the Gekko, all of those optimisations should still work!  There also won't be any struggling with the new technology like on the other systems with 6 threads and such; Retro can just go nuts without worrying about efficiently using extra cores and such.

2-Retro studios has had since Christmas 2004 to work of Prime 3.  That's a full two years, while normally launch games are thrown together in about a year or so, making this a very long development time relatively speaking.

3-The controller will simply kill.  Metroid's a great series because it's so atmospheric and makes you feel like you are there.  With this new controller, aiming samus' gun in real life with your own arm will bring this great series to a whole new level, and nothing will be able to compare.

4-Metroid Prime 3 will be a further refinement over Prime 1 and 2, which is a reason in itself to get excited, since the first two looked great, had moody music, and great gameplay.

So there you have it, Prime 3 should rock because it'll be a great showcase for what the Revolution can graphically do, it won't be a rush job, the controller will blow gamers away (especially for this type of game), and because Metroid in general kicks butt!