I didn't start with D&D. I started with Marvel Super Heroes, then put out by TSR. This was before the 'Advanced' Version. I did it because I loved super heroes and comics in general.
One of my friends showed me the 'other' game that TSR made, AD&D. He had a bunch of Role Aids books (by Mayfair, before the old d20 revolution), basic D&D books, and some other stuff. We didn't have all the proper dice the first time he showed me to play, me having only d10s for Marvel and some d6s from other boxed board games but we improvised pretty good. I was caught between Asmodeus and Orcus as they fought to control a dungeon.
Having loved the Hobbit and other fantasy style books, I was hooked pretty quick. I've played other games including Rolemaster, Call of Cthulhu, Fantasy Hero (and Champions!), as well as a ton of others I can't recall right off the bat (Runquest, Elric, Warhammer FRPG), but D&D has the most support and it the most commonly played game. In some ways, is it the game system. I'm more comfortable with it's spell system of unique spells as opposed to list spells. In many ways, it is the support. The d20 hoard allows me ot have game mechanics for almost any idea I want. Does that make D&D perfect?
No.
I don't think you'll ever be able to handle an Exatled style game right off the bat with D&D. Could it be done with the d20 mechanic? After seeing Conan, Midnight, Grim Tales, and Mutants & Masterminds, I'm sure so. But much like those games, it's not D&D.
I enjoy the social aspects of D&D too but find that as long as people as 'cool' with one another, the socialization isn't the top priority.
I also enjoy the 'graphic' part of D&D in terms of art, layout. I enjoy the 'collector' part of D&D, buying new books, getting miniatures, painting them and moving on from there.
In short, there is no 'one' reason I enjoy D&D but many and I'm fortunate enough to still have time to enjoy it with a good group and still have my friends who enjoy it and occassionaly get together for it.