It seems that in all the comments I read across the Internet, amongst the chorus of "THIS MOVIE SUX!" there's a small faction that says "I didn't think it was so bad." I'll be that guy for this board.
Don't mistake that for praise, I just don't think it's worth lumping with the dregs of the genre (Green Lantern, Fant4stic (wherever the Hell the 4 goes), Elektra, you know the rest). I think it's some good editing away from being a movie that wouldn't have made online bashing the e-sport of the week. By that I mean there were some really good moments, some really good scenes. Unfortunately those were followed by scenes that filled me with thoughts of "wait... what?" I can think of 2-4 scenes that simply deleting them would have added 2 more points (10 point scale) to the score. More after spoiler embargo...
As to Affleck specifically, I kinda feel bad for him, he doesn't deserve to get dragged down by this movie. I put him as the #2 Batman (Kevin Conroy #1) and an upgrade over Christian Bale. I hope his solo movie does much better, likewise for his Suicide Squad role, whatever that may be.