I don't understand when people say "Tupac was good, just not lyrically (as) deep (as Eminem)." It's as if they haven't heard any 2Pac songs, at all; except his posthumous releases. One person commented on here that 2Pac's best song was "Changes", which shows me that that person has no idea what they are talking about whatsoever. If he did know, he'd know that song was butchered between 2Pac's other verses, like a part of a verse from "I Wonder if Heaven Got a Ghetto". Whatever.
Anyway, I mostly agree with Darth Karath; although Eminem has great lyrical ability, he has a very limited subject span- a lot of his albums aren't diverse. Some of his albums just sound like repeats to me, to be honest. In comparison, there is no comparison. Eminem is not even on the level to be considered amongst competition for the best alive, let alone better than 2Pac. However, most of the people on here have never even heard of 2Pac, much less ever listened to his music (one user mentioned "growing up listening to Eminem. Nuff said).
A better comparison would have been Jay-Z and Eminem. We could go at it for days with song examples and opinions and yet still be interesting. It's like Apples and Oranges with them two. But Pac and Em'? That's like Gold and Copper. We're asking people to make decisions they aren't even fully aware of. That's like asking them who's better between Juice Crew and Boogie Down; they'll look and go "WTF" and vote for whoever they are more familiar with.
TL;DR: 2Pac gets my vote.