Well this is exactly what HHH said about Sami in the NXT conference call yesterday. That he's not as flashy as someone like Neville (though Sami does do lots of spectacular things), not as fancy looking as others, so he might not be as instantly over, but over time he gets you invested in him emotionally, and while it's a slow burn, you are absolutely behind him by the end.
And this was just the proof. Look at how 100% in love with him the crowd was, how often have you seen a crowd this completely behind a babyface? Not a lot.
Basically Sami is a slow burn kind of character, but the payoff is worth it.