Spider-Man has got to be my favorite superhero of all time.
Why is that?  What do you like most about spider-man?
The whole orphan dynamic with him in the Marvel Universe is one of my favorites.
I've always wondered why Stan Lee made him an orphan?
I'm not sure honestly, him being an orphan makes him a bit more of an interesting character, especially compared to other Marvel heroes. 
I suppose it's easier to be a superhero without family ties.
Yeah and this also allowed him to be depicted with normal struggles of adolescence.
I think you are right!  Superman and Harry Potter were orphans too.
Yeah they were! He also deals with stuff like financial issues.