Lyrics all the way, Babyyyyy!!!!! 
I do like when the instrumentals accentuate or represent the meaning of the lyrics. That synergistic combination is what makes a song very memorable to me. However, if I like the lyrics and don't much care for the music, I will still probably enjoy the song.
If the lyrics don't interest me or make sense, then the song usually won't engage me very much. An example of such a song is "Kissing the Lipless." I love the song's sound, but it doesn't have a deep impact on me since I don't understand the lyrics, which seem about some trivial relationship topic. Of course, I do like Trio's "Da Da Da" song immensely...so maybe I'm just spoutin' crapola here.
Two songs where I enjoy the lyrics by themselves but *especially* combined with the instrumentals are these:
(1) Don Henley: "You Can't Make Love"
You Can't Make Love | Don Henley Song - Yahoo! Music
This song wouldn't stand out in my mind due to the instrumentals, but I love the meaning of the lyrics. They say that you can go through the motions of what you would do if you loved someone, but you can't *make* yourself feel deep love for someone, and you can't make someone love you. A good life lesson said succinctly in a song.
My favorite part of "You Can't Make Love" is at 1:34...this is actually one of my favorite moments in ANY song...when Don Henley sings, "You can...(PAUSE)...go through the motions." The feeling of waiting and wanting and expectation builds up during the pause...until at last he says "go through the motions." I could listen to that moment in this song around 100 times. And have!
(2) Tool: "Right in Two."
Good lyrics that make me think + Good Instrumentals = Great Song.