Sports games get stale, and are only open to a select audience. Much like racing, it is important to have a simulation and an arcade style to appeal to different audiences. Sure, NBA Jam exists again and NFL Blitz was meh. Both were tied down by licensing issues, and ironically both were done by EA. While it's nice to see these two again, we do not necessarily need licensing to make great games. In the 90s, EA actually created some really interesting games called Mutant League Football and Hockey. You can also throw in NHL Rock the Rink as well. Mutant League mirrored their professional counterparts, but had teams that poked fun at real life teams. People I talk to now that aren't sports fans do remember playing those games, and most would enjoy another iteration of the titles.
The scopes of games have changed with the internet. Games like Little Big Planet and Modnation Racing have changed the scope of replay value in games. With the ability to customize your characters, or download others, it allows for endless hours of entertainment. Even if you lack the creativity or effort to create something on these titles, there's always someone else who does. Imagine you make create a team and all the players are the X-Men and they are beating up and doing stupid things against a created team of Nascar drivers? The idea of having a sports game that's over the top, and allows for customization would be ideal. It could also give a developer and opportunity to show off a great graphical or physics engine to maybe help it's case in acquiring an official license.
As for the game itself, if it's football or hockey, the game would need to be brutal. No blood necessarily, but comically brutal. That's part of the problem with the new NFL Blitz. The NFL doesn't want to make this available to make themselves look bad. A developer without a license could basically do what they want. I mean, you could make it bloody to where a QB sack would involve pulling the QB's head off, much like a Mortal Kombat fatality. Hockey would have to be overly brutal, fast, and include tons of fighting. Wayne Gretzky Hockey was an amazingly fun game for the N64, and so was NHL Open Ice. Mutant League Hockey was the over the top title people loved to play.
Blitz: The League even had a nice run and has a cult following, but that game was more of a dark take on the sport of professional football. Nothing needs to be dark and disturbing about the game. Twisted Metal (my PS3 game of the year) was rebooted and was amazing. The sports title doesn't need to be like that, but it's a good example of over the top combat. I think EA should resurrect Mutant League Football/Hockey or another developer step to the plate with something of equal value. There's a lot of potential with this idea to help lure casual fans into sports games.