Clark and Diana is numero uno.
Other pairings I could go for...
Bruce/Selina
Bruce/Zatanna
And I oddly enough wouldn't mind seeing him explored with Black Canary. The street level characters suit Batman and his world and the ladies all visually compliment him nicely too.
I wouldn't mind seeing Dinah with Hal Jordan too. I really never into Carol Ferris.In fact I really don't get excited much for the civilian type love interests like Lois, Iris, Linda etc etc. I don't care for Ollie/Dinah either. Maybe Arrow the tv show might change that. (He's a hottie btw...and looks like he'll eclipse Tom Welling's Superman easily in the sex appeal /interesting character dept...honestly, in hindsight could Smallville have really created a more boring and less charismatic Superman?

...but doubt I will have the time to follow Arrow)
Wally West I would love to see with Donna Troy one day. (Blame Donny for that)
Conner/Cassie, I guess? In YJ I really don't much care for the Miss Martian build up and their dynamic too much. I wish Conner gets someone else in YJ. Cassie is going to be with Blue Beetle I see. She's much younger than Conner so unlikely they'll hook up in that show. Conner is Hot. He looks like a young Kal, you know.
Not too sure about Black Adam. Guy's a mass muderer.
I always thought Rip Hunter sexy. And Hawkman. And Kyle Rayner is cute too.
Dick...hmm, he's got a host of girls, hasn't he? I don't mind them all...except Kory. I never cared much for Dick and Starfire.Just don't get that one.
Anyone into Legend of Korra? I have been kinda off and on watching it. It can be a little boring at times for me since not to into Avatar mythos etc but I was kinda baffled they pushed Korra with the cliched badboy troupe Mako. They so boring once they "hook" up and there was something very empty in their dynamic. But he's cool cuz he's moody so I guess one should not be shocked. Funny how cartoons can teach young girls to go for the worse love interests. He was two timing two girls. yeesh. It's just like WW chasing desperately for Batman to give her some attention.

I felt Korra would have been way better with Bolin, who was just plain fun and loyal and clearly loved her for who she was.
Other...Modesty Blaise/Willie Gavin
Thor/Sif
Conan/Red Sonja
Eliza/Goliath
Xena/Hercules
Angel/Faith