1. His dorky exterior is just a mask for his inner hunk. Artie is a stud. Let's be honest, the dorky clothes don't hide that he's attractive. I love his attitude. It's hot.
2. His confidence. Artie sings great and a lot of what he has is confidence. He really goes for it, which I have to say is something I don't hear in Finn's voice as much. Push it is the perfect example. He's completely confident being himself and saying what he feels.
3. His positive attitude. He has all this potential of being singled out by the jerks in school, yet he's probably the most upbeat member of the group.