I went synthesis as the canon ending for my paragon Shep. I'm currently doing a playthrough of the entire series and I'm now at the third game. I'm going renegade this time though, so I think it'll be control for this Shep, as she saved the Collector Base in the second and the attitude of controlling the Reapers, instead of destroying them hasn't changed, despite Cerberus being a bit out there.
EDIT:
MiloP said:
It's weird, people keep claiming that there are only three endings, but there's actually quite a bunch. Sure all of the cutscenes look the same but considering you're technically only supposed to see one that then becomes the canon ending for your particular Shepard, then it ceases to become a major problem, really.
Thank you. I've been saying that as well, but people won't admit that they are different endings.