1) They make marriage cool.
Marriages are notoriously portrayed in television to be at best cumbersome and at worst expendable. In many shows, the staple couple either gets together early and constantly breaks up (Ross and Rachel) or the writers take the entire series to put them together (The Nanny). To see a television couple actually get married, start a family, and stay together is rare in the world of the half hour comedy.
Jim and Pam have certainly not had a perfect marriage, but their pretend marriage expresses the qualities that real marriages should be built on: family, mutual appreciation, trust, a sense of understanding, and a sincere friendship. That's just a few elements. Didn't you want to cry when Pam found that list? I'm not going to lie, I welled up a bit. So hats off, Jim and Pam, for making marriage decently fun and not at all cheesy.
2) I can actually relate.
A "Jim and Pam" love is completely attainable, unlike many unrealistic and superficial movie/TV romances (*cough* Twilight). I'm not saying Tim and I have exactly the same story, but it is similar (he liked me, I was with someone else, he waited, we became friends, then best friends, he told me how he felt, I said no, we stayed friends, I changed my mind, and in a nutshell here we are!).
I never consciously thought that the guy I was with had to be everything that Jim was, but I knew I wanted someone like Jim; a guy who was my buddy, who was gentle but funny, who thought I was the coolest even though I'm super lame, and a guy who just "got" me and liked me the way I was. Tim and I are definitely not perfect, but one thing I can say with full conviction is that I have always (always!) known in my head and felt in my heart that he likes me exactly the way I am.
Here's to my Jim Halpert, and here's to finding yours. :)