I didn't like Steely Dan for the longest time. Granted, being born in the late 60s or early 70s is especially a curse for Steely Dan appreciation, because by the time you're at the age where you really get into music as a kid, which is when disco, punk and new wave have ascended, Steely Dan becomes a cultural joke. The first time I heard the name Steely Dan was watching a lot of stand-up comedy on TV in the 80s with comedians making jokes about Steely Dan with respect to elevator music.
Sometime in the late 90s, when the Steely Dan reissues on CD came out, I listened to the debut Can't Buy A Thrill, which is probably the best starting point from a classic rock perspective. I soaked in that album for a while, and I eventually loved it. I moved forward chronologically slowly and became a fan. That said, I truly understand why some people never want to open that door and walk in too far.
I'm STILL trying to get into The Grateful Dead, for example... starting with those early albums up until 1970. I like them a little more now, but they still don't impress me yet. This is all a personal battle with me. No one has to try to get into anything just because others are bought into it.
EDIT:
maybe someone give a 5 song gateway thing.
These songs might be obvious more or less but:
* Dirty Work
* Midnight Cruiser
* Show Biz Kids
* Any Major Dude Will Tell You
* Barrytown
I think Pretzel Logic is the best gateway album actually.. it has the shortest, poppiest songs, and is the best "indie pop" intro to the band -- meaning that it's the mostly jangly, sugary, least showboaty Steely Dan album.