I don't think so. He might flip some moderate Jewish voters who wouldn't otherwise vote GOP, but otherwise I don't see how he could help the ticket. Jewish voters are a tiny minority of the total number of voters in this country (as the 2000 election showed when LIEberman only helped Gore win in a couple of select areas like south Florida) Cantor is from the safest GOP district's in Virgina and won't change the results from how Virgina is going to vote anyway, as the votes he gets in his district each election are hard R voters. If McCain's going to beat a running mate from Virgina, the first criteria should be someone who win over parts of Virgina that aren't automatically going to vote GOP. We need to keep VA's electoral votes in the GOP column or we're toast.
I think Cantor would probably make a good VP, but he wouldn't make my top 10 by any criteria. He's more valuable staying in the House to fight Pelosi & Co.
If McCain wants the Jewish vote, I can think of a certain senator...