Do you think he ever showed this level of ability (which would make him the greatest pace bowler of all-time)? If so, which year was it in? When I'm talking about peak, I mean the best 1-2 years of a player's career - for instance, as long as McGrath's peak was, he was really at his best in 2000.
More importantly, what kind of stats do you think Waqar could have had? Total wickets, wickets per match, Bowling Average, Strike Rate and Economy Rate? I sincerely doubt his Economy Rate could have been superior to McGrath - his best Economy Rate in a year (and when I say peak, I mean 1-2 years) was 1990 when it was 2.63 (although his peak Strike Rate, in 1993, is simply sensational - 29.5 - this might well be the lowest Strike Rate of all-time for a one-year period in the modern era). On the other hand, McGrath spent 10 years with a lower Economy Rate than that.
Here you go:
1990: 49 wickets @ 17.04
1991: 7 wickets @ 18.14
1992: 13 wickets @ 22.87
1993: 55 wickets @ 15.24
1994: 42 wickets @ 21.29
Total: 166 wickets @ 18.02
More importantly, one had to see him bowl to get an idea how good he bowled. I clearly remember in those 5 years he had most of the wickets either clean bowled or plumb LBW in front of the wicket. I also remember he was a victim of quite a few missed chances by his teammates throughout his career as a bowler (so was Akram, too). Give me a bowler like Waqar 1990-94 in my team, and as a captain I would be anticipating a wicket every ball. Every time he turned at the top of his run-up there were adrenaline flowing all over in the stands and in front of the television sets. He could get you a wicket in the 2nd over with his fierce out- and in-swing, in the 20th over with his sheer pace and banana inswinging yorkers, and in the 30th over onwards with his lethal reverse swing. You could count on him to wash off the tails in no time. It's not a big deal that the best of batsmen feared him, the big deal is that they feared him always regardless of the match condition, pitch condition and ball condition. And his pace was not the main thing for which they feared him, though he was as fast as anybody in the world then.
Well, if Waqar was not so injury-prone, if he wasn't a victim of the craziness of PCB and politics by...errr...a few of his teammates, if he had the 'mentality' (pardon me for using this word, I know this is not an appropriate word, but I couldn't find a better one...probably 'mcgrath-ish or tendulkar-ish mental stamina' would have been better) to continue to be at the top for as many years as he could and if Pakistan played as many tests as Australia then he would easily end up with more than 600 wickets @ 19 or so (chucked in some imaginary numbers only because you asked). And would surely be successful in all conditions and against all kinds of batsmen. You can easily gauge the no. of 5-fors and wickets per match he would have grossed then. As per strike rate and economy rate goes, as a statistician I regard those 2 stats as the 2 most useless in test match bowling. Still, you could easily gauge his SR in that case (given where it stands in reality). His ER wouldn't have been as good as McGrath's. Had he achieved all these his career spanning across the 90s and the early 2000s (yes, I quoted those figures keeping the quality of pitches and batsmen in mind), he would clearly have been the best fast bowler in history in my book...better than all of Hadlee, Marshall, Barnes, McGrath, Imran, Ambrose, Garner, Akram, Lillee, Lohmann, Holding, Trueman...and by a comfortable margin.
Disclaimer: I don't consider Waqar to be one among the best 10 fast bowlers of all-time.