I think Steyn should be higher up than he is. He has a strike in the early 40s...in today's era of flat tracks and with all the crazy good batsman around the world. And he doesn't stop taking wickets. I'd rate him higher than a lot of other greats who played in more bowling-friendly wickets against batsman who didn't have helmets and when an average of 45 meant you were godly. Same reason I rank Waqar higher than Wasim (though I've never watched either of them). Even Shoaib had an insane strike rate and it was still far higher than Steyn's. Only man who could match Steyn's penchant for wicket taking was Shane Bond.
This is purely a statistical thing, but I think at the end of the day that should count most heavily.