This one may surprise you. Or maybe it won't, if you've seen the complaints I level against a lot of villains in stories these days. For Favorite Rogues Gallery, I'm going with. . .
The Rogues themselves!
I considered the Bat-villains, and while I do enjoy the Riddler, and some of the other guys off and on (Gail Simone wrote a good Bane, though he wasn't being much of a Bat-foe at the time), it feels like there's too much focus on body counts with them these days.
There are more than a couple of Spider-Man villains I like, but Norman kind of got killed from overuse, and a lot of them are so hellbent on revenge these days that it's kind of a turn off. Plus, there was this panel from Deadpool Annual #2 last year, and it's kind of hard to argue with Wade's assessment.
It isn't that you can apply those labels to the Rogues as well. Some of them kill, they can get fixated on revenge on the Flash, and Wally (sigh, or Barry, I suppose) can use the "champion against dumb" line themselves pretty easily (Guy with cold gun, guy with hot gun, weather magician, April Fools' Bro, Aussie stereotype).
Some of this is confirmation bias. I've never bought The Flash on a regular basis, so I'm mostly going off what I see on the Internet, which is mostly people gushing about how cool the Rogues are. That they aren't out to conquer the world, or drown the streets in blood, they just want to make a little bank. They aren't normally after the Flash's head, but if he shows up to interrupt their latest heist, sure, they'll take their best shot at kicking his teeth in. It's not personal, though. Even if they aren't bosom chums, there is a certain amount of respect and camaraderie among them, provided you don't violate any of their rules. If you do that, they'll probably kill you, because bad guys, but otherwise, sure, let's hang out and drink beers together.
Every so often, somebody does a story about Spidey villains hanging out in a bar drinking, but by and large, even when they have a team-up, they aren't really pals. Doc Ock was always betraying the rest of the Sinister Six, or strongarming them into helping him, or turning the Sandman into glass and breaking him. It's not a prerequisite for the villains to get along, but it's a particular quirk of the Rogues that I enjoy.
Also, Captain Boomerang was one of the (many) wonderful things about Suicide Squad, so the Rogues earn bonus points for counting him as a member. I suppose that Deadshot should be earning bonus points for the Bat-foes on those grounds, but I don't really think of him as a Bat-villain, for whatever reason.