Madden ONLY sells because it's the only football game out there. I'd say they sell on reputation but the positive reputation it has is all the way back to 2 system cycles ago. NBA 2k was bare bones in terms of features but if anyone tries to act like that game isn't amazing on the court you're lying to yourself. It's year 1, i'd rather have a game like NBA 2k with more barebones features and amazing gameplay than have a ridiculously in depth feature like Owner mode but awful gameplay like Madden has.
NBA 2k will have a much easier job in the next few years adding new features and game modes and adding things to the game because they have amazing gameplay locked down. Meanwhile Madden is always going to be a disappointment because many of the ugliness from last gen is still there on current gen. So Madden needs to wow you with features to take attention off the on the field issues. Madden wants you to spend more of your time on the off field stuff making the on field stuff less of an issue but when push comes to shove the gameplay is the most important thing.
So again, i'd rather have a game come out year 1 and nail gameplay and be bare in terms of features than a game be packed with features but have bad gameplay. There's a reason I can keep playing NBA 2k over and over again but with Madden everytime I turn it on i'm bored within 5-10 minutes.