Story: ME3 > ME1 > ME2
ME3 takes this for me due to the depressing tone and and some really quite brutal events. You really get the sense of foreboding during the whole game whilst the story has a great sense of scale. It really conveys the helplessness of war and existence itself. ME1's was boringly traditional if you'd played a Bioware game before. The story meandered from one event to the next, following the same tried and tested tropes and formulas they'd used in all their previous RPGs. ME2 was different but the over arching story is relatively simplistic once you take out the smaller, more personal side-stories that the game was built on.
Gameplay: ME3 > ME2 > ME1
This should be a no brainer. The shooting mechanics in the original were terrible with stupid ally AI. You could play it as a more traditional turn-based RPG (defeating the point of the shooting) but a pretty poor one at that. ME2 greatly improved in all areas of gameplay mechanics although simplified the RPG systems a bit too much whilst ME3 further improved the mechanics and balanced them with more RPG elements.
Characters: ME2 > ME3 > ME1
ME2 first because the whole game is centralised around discovering the party that you build up. Most of the story is centred around their personal motivations. Then you have characters like the troubled but hilarious Mordin, a deeply religious dying man in Thane or the psychologically damaged, Riddick inspired Jack. The second choice was a lot harder as part of the reason ME3's characters are good is because of the events of 1 & 2, but it just takes it for me.








