I will always be mad about the ME3 ending. If reincarnation is something that happens, my reincarnated self will be mad about the ME3 ending from birth.
The endings didn't take into account any of the choices you'd made up until that point. The endings were also a bit brief before the ending patch. I think those were people's biggest complaints, I could be misremembering.
Highly recommend the trilogy! Great story, amazing characters, pretty great gameplay (especially after #1), and overall an immersive journey. I wasn't bothered at all by the ending, personally.
What a godamn waste.