im glad someoen else bumped this because i didnt want to be the oe to after i finished it (much later then the rest of you).
i didnt think it was a terrible game. it didnt quite draw me in as much as the first two but i think its because i rushed it and NOT the voice acting and characters that interact with you.
In the first Prime games i didnt really know what the game was going to be like, i had never played a metroid game before hand (well i did, but not more than five minutes) and i first played prime borrowed from a friend. the Scanning system was intriguing but i didnt realize how important it was to not only the gameply but the story, not until i bought my own copy anyway. I loved it and i knew i had to by Echoes when that came out. I loved how tough it was and there's still some Lore i havent found in both games. How are you supposed to explore and try to scan everything when the atmosphere kills you! ah, so great.
then comes prime 3, at a point in life when i have less time for video games. After 2 entries into the [prime] series i knew what to expect but that wasnt a bad thing, because the formula was good and made even better by the motion controls. Because i had to limit my time playing i did everything as fast as i could (yet still managed to scan all but 2 things, literally) and by the end i finished under 20 hours! the first two took me over 24 on my first play throughs. i was pissed too, 99% items collected in 17:24!!! where was that one missing item, argh!
anywho i think some of the ease that came with playing was in the level design. i think because the game was set up in stages it was easier to explore every nook in cranny because you wouldnt end up in another area. ie If im wandering around Norion, i'm gonna stay on Norion. whereas in Prime 1 i could be in the ice area and end up in the fire area if you werent paying attention to which elevators you took.
the other thing that you could argue made the game easier then the last was the fact that you always knew when you were going to fight a main boss in the Leviathin Cores. it was much easier to prepare for a boss fight and the battles themselves werent as unique as they could of been because they layouts were always the same. To this day my favorite metroid prime boss fight is that huge bug that flies over the acid lake while you swing around from platform to platform. there was nothing like that in prime 3