My Perfect ending the the Mass Effect series would be to epic to compelety but to words, so I'm gonna shortin' it for ya' ^w^ . . .
1) Earth gets Blown up(for all the LoLs).
2)Harbinger and all his little reaper groupies end up dead somehow.
3)That Anderson gets to smack the stupid Turian council member after all the years of "Aw yes, the Reapers" crap.
4)The Geth help end the reapers and become a actual race (allought that probaly way far from what happens X'( ¿POR QUÉ ?!?!?!?!?).
5)Wrex reunites the Krogans into an Empire (Wrex being Lord Sidious and Grunt as Darth Vader or some uber cool crossover shenanigans) and get a spot on the council.
6)I know I'm gonna get trolled for this but It would be awesome if Saren and Nihlus could come back . . .

7) To shut up the whinny Quarians I guess they could have their home world, but me personally couldn't care less about them >:3
8) Liara and Feron help Shepard with all their cool job at knowing every secret deal, Shepard kinda did just give it to them.
9) That a relationship with Garrus becomes serious and we get to meet his family, show big daddy V who's the Boss! HA!
AND Finally 10) Shepard lives. I'm not giving up over 5 years of my life, over $100 (First two games + DLC), and all my hopes up into a hero that dies in the end! No way in HELL!! It would be cool if Shepard lived and came out with a robotic limb or two.
. . . I could have written more, but a got a page on my omni-tool. LoL JK.