I see Yahtzee read my opinion on Lex Luthor. Yes, we definitely need a movie for him. TBH I don't even care about the other villians. Batman villians change so drastically with each adaptation, that I can barely call them by their names. I liked Bane's backstory. Not TDKR Bane, but maksed wrestler on Venom Bane. However, they will never make a movie about the villian when the audience usually doen't know of their existence without the hero. It's just like Transformers. In our niche, here on the internet, it may seem like everyone knows this stuff and it would totally sell well. Not true. Without "Superman" somewhere in the title (or common title, i.e. Man of Steel) the VAST majority won't know it takes place in the same universe. And then once they find out, they will complain why Superman wasn't in it at all/enough (pretty likely chance of that is you saw TDKR reviews).
Actually, how did that all work in Smallville? I never saw a single episode, but it sounds like the kind of thing that would have hours worth of Luthor talking to himself in order to give off more exposition.