Don't know about you, but I think a number of previously good DC books have nose dived in the last year since creation teams changed. I give you Flash, Wonder Woman and Green Arrow to name but three and also the Green Lantern comics are hardly setting my world alight since GJ left. Batman soldiers on in excellence, so what is the best current DC comic that isn't a Batman title? Justice league?

Justice League

Action Comics and Superman are really good right now. Of course Geof Johns is leaving Superman so my are fingers crossed it stays good.

Best book that doesn't star batman: Grayson

Best non-bat-book: Swamp Thing

Best non-bat-book continuing after convergence: Justice League

Justice league, aquaman & superman

I think the ones you mentioned as nose-dived are some of the pretty good ones. People give Kreisburg and Sokolowski crap, but I've greatly enjoyed their GA arc. The Flash and Green Lantern have also both been pretty darn good under Venditti. About on par with Aquaman, which is also really good. And while I don't read Grayson or the main Batman title, I've been finding both Batman & Robin and Detective pretty average. I'll grant you that since Meredith Finch took over WW, it hasn't held a candle to Azzarrello's run, but it's not too bad and has plenty of room to improve. She's new to the DCU, so I'm giving her every opportunity to do the job right. Unfortunately, as good as Azzarrello's run was story-wise, he pretty much mucked up the Wonder Woman character and Finch is rolling with it.

Honestly the best titles DC is putting out right now are their three weeklies. With the exception of some parts of Futures End, these have all been consistently great. And I'd of course have to mention Geoff Johns' run on Superman and Jeff Lemire's JLU. I've also been enjoying both Trinity of Sin and Aquaman and the Others. Lobo, Worlds' Finest, and JL3000 all really suck though. And though many people are head-over-heels in love with Pak's two super-titles, I have found them pretty awful most of the time

JL and New Suicide Squad are up there for me.

Justice League Dark, Justice League, Action Comics, Earth 2, Supergirl, Grayson, Batgirl, Swamp Thing, Green Arrow are all better than the Batman comics except for Snyder's Batman.

I presuming your questions means books that really don't feature Batman as a main character. If that's the case my list would be:

Grayson, Aquaman, Action Comics, Superman, Gotham by Midnight, Batgirl and Justice League.