I can say who I think NRS would like to be in the top 5. Whether they'll ultimately be successful, I don't know.
1) Superman: Superman is, well, Superman. He is definitely supposed to be one of the best, if not the best. Man of Steel is the hot commodity right now, Supes v. Batman is hype, and, most of all, Superman is the main villain! Wouldn't it be stupid if you fought through the Classic Battle to get to Superman and he wasn't the toughest in the queue? And LBSH, you could nerf the heck out of Supe's trait and he would still be gdlk.
2) Batman: Hey, everyone loves Batman. A lot of folks would buy the game just to play Batman. No one wants to hear Batman sucks, oh you shouldn't play him. They want Batman winning tournaments. Again, Superman v. Batman is all the rage in the upcoming movie, so, Batman must rock. Really, the core of the Injustice plot is Superman v. Batman. Batman needs to be awesome. When people say, "best trait in the game" they are probably high-fiving at NRS.
3) Aquaman: Aquaman is a "new" character (not in MK v. DC) and they want people to play him. Boon said early on they were trying to make the coolest Aquaman ever. I don't think it was a mistake that Aquaman was seen right out of the gate as awesome and still awesome post-nerf. They want Aquaman to be a contender, for sure.
4) Wonder Woman: Just look at the number of skins!!! They want her to be played. Wonder Woman was in the demo. Also, she is kind of a counterpoint to Aquaman in the Flashpoint series, so they should both be way up there. If Aquaman owns, WW must own too. It would be crappy if the top 5 was a sausage fest, so I think NRS would like to see some Wonder Woman tournament victories. It would be kind of sexist if the boys could whomp all the girls, so there needs to be at least one female contender and WW is the obvious choice.
Runners-Up
Black Adam: NRS might not want to be accused of over-nerfing. Also, technically in the lore Black Adam is hardcore and should be able to give Supes a run for his money. They might want at least one villain up there.
Doomsday: He was scary in the demo. I don't think that was a mistake. Doomsday should be scary and able to give Supes a tough fight. Ditto on maybe wanting a villain up there in the highest echelon.
Flash: Buff after buff after buff. Someone at NRS obviously has a hard-on for Flash. He was one of the best in MKvDC. Flash fans are a die-hard bunch, and there are clearly some Flash fans at NRS. Not to mention, in the lore he is extremely powerful. Also, there are already plans to have Flash appear in Arrow Season 2 so they can spin off a Flash series starting in 2015. I think stuff like that matters.
DLC Characters: You might not want the top 5 to be all pay-to-play characters, otherwise it is pay-to-win which no one likes. Yet, having a Zod, MMH, or other in the top mix means increased $$, so they are almost always going to be good. In MK, standard characters like Kabal and Kung Lao might be at the top, but we see DLC like Kenshi and Freddy nipping at their heels.
