I almost don't want to see Looper after finding out the director/producer/writer/actor of Primer was asked to be an advisor for the time travel elements. Both Back to the Future and Terminator did it perfectly fine.
Looper explains time travel less than BTTF and Terminator. The most explanation you get is Bruce Willis saying he's not going to bother explaining anything.
End of Days - worth it just to hear Arnie call Satan a choir boy