I agree with phlint, and also because people are used to seeing toplist sites listed from top to bottom. Don't see many top 10 lists of any kind that are not simply stacked (rather than left to right).
I would stick with it. However, with some programming you could do tabs... something like...
Rank1 (of TAB1)
Rank2 (of TAB1)
Rank3 (of TAB1)
So that when they click "Tab 2" they get the Tab 2 list in place of Tab 1's list, like this...