1. They're never too good for you.
2. They lend you books and cool movies you never would have thought to see.
3. They have this whole Klingonian/Knightly honor thing going on.
4. They don't bug you about your appearance.
5. They practically worship the ground you walk on.
6. They're willing to try anything just to make you happy -- and to enjoy it!
7. They're not afraid to do some things that might seem a little odd -- they've been odd all their lives.
8. They know how to fix things.
9. They're generally available, and slutty girls aren't apt to harass them and try to steal them away from you.
10. Other people (who aren't so hung up on social culture) think he's great because he's intelligent and can get into a decent conversation about, oh, say, the intricacies of any number of musical genres, of cinematography, or of the merits of dual-CPU systems and differences between OS's.
11. They have the coolest toys. (Fingerprint scanners? Hello?)
12. They can be counted on.
13. They're interested in a future for themselves (aside from getting high and hitting on the same people all the time.)
14. They're gallant and thoughtful; mostly I think it's because they can't believe you're not dating some dashing, tall, handsome, rich guy.
15. Their egos are not larger than their heads (when it comes to girls.)
16. They can be trained. The downside is that you have to put time and patience and work into getting them set properly as 'boyfriend', but it's a lot more rewarding.
17. They have the best jokes. (Highbrow humor nobody's thought to tell you before.)
18. They're easy to keep track of.
19. They're more mature. (Sometimes!)
20. They're rarely anything less than perfectly sincere. (In not participating in much of popular socialite culture, lots of them didn't learn how to lie well anyway.)
21. They don't need their egos massaged. That's what building things is for.
22. They've got imaginations.
23. They like to work with their hands.
24. He can think his way out of a jam (and thusly will rarely call you to ask for money for bail.)
25. Anguish during adolesence made them kind-hearted and unwilling to treat people badly. (Except if they treat The Girlfriend badly!)
26. They're genuinely grateful for female attention.
27. Parents love them.
28. Being as oftentimes they're up late at night, most of them have figured out how to cook well.
29. They're good listeners.
Anybody want to add more?