McGrath would be in my top ten probably. I'm going off people who have seen both bowl who all seem to rate Lillee more. It took McGrath a few more matches to get the same number of wickets, and Lillee probably played slightly better opponents.
None of this is denigrating McGrath who is actually somewhat underrated IMO lots of people talk about him being a machine, a metronome etc, using those terms somewhat negatively. It underestimates him.