Based on peak rating, Wasim isn't even among the top 75 bowlers ever. He was also outside the top 5 in the world rankings for about 75% of his career.
ICC Player Rankings
www.relianceiccrankings.com
Quite surprising given his undoubted talent and ability to do almost everything with the ball. Having said that, obviously ICC ratings are purely statistically based and while many of his peers rated Wasim as the best bowler they ever faced, the stats just don't back it up. Wasim's WPM is relatively mediocre for an ATG and a high proportion of his wickets were tailenders.
Don't get me wrong - a test average of under 24 and the one time world record for ODI wickets shows he certainly was a fine bowler. But there were a number of bowlers in his own era who got better players out more often and more cheaply (Marshall, Hadlee, Ambrose, McGrath, Donald).
Some say he could bowl 6 different balls an over with perfect control and without a noticeable change in action or wrist position. But if another player with less variety can get better players out more frequently with a single lethal delivery (Waqar's in swinging yorker?), then the latter bowler is actually going to win you more matches.
Some of Wasim's contemporaries, such as McGrath, Ambrose and Waqar, were able to run through the top order of quality batting lineups on a fairly regular basis. Wasim did this a few times, such as against Australia at Melbourne in 1990 and Karachi in 1994. But he did so very rarely, and unlike the bowlers mentioned above, you really need to search far and wide to find such examples. Despite the imperious reputation he appears to hold amongst his peers, Wasim simply was not as consistently destructive.
He certainly had a massive box of tricks and was one of the most skilled exponents of swing bowling ever seen. But at the end of the day, a number of his contemporaries who could NOT do all that and did NOT possess that skill level were more effective matchwinners.