I think people still love Will Smith and he's still one of the few "movie stars" we have left. He's not one of those actors that puts out a film every year so when he does decide to do a film people pay attention.
I personally just think Will needs to stop doing these dark, dramatic roles and get back to doing roles that utilize his fun, charming personality. All the best Will Smith movies are the ones where Will is acting like himself. Hancock was crap, Seven Pounds was depressing, I didn't bother with After Earth, I am Legend...wasn't BAD, but wasn't great either (imo). Focus was a step in the right direction, I think. I really liked that movie and I thought it was a return to form. I'm not looking forward to Concussion because it looks like another attempt at Will trying to go dark and I just don't think that works out for him. I think Suicide Squad will be a true return to form and give us the charming, badass Will Smith from the 90's back.