As Glitch said, many greats have missed significant time.
With that being said, I wouldn't go so far to say "who cares". Context does matter, and let's get real, Sid had some really freak injuries happen and much of his lost time came at the absolute prime of his career, between ages 20-25.
Steckel ruined Sid's greatest peak year and certainly cost him a Hart, Ross, Rocket, etc in 2010-11. When you adjust for scoring levels, I think that would have ended up being the 2nd best offensive season post lockout in 05-06, even if he slowed just slightly from the pace he was on (64 goals, 132 points) through 41 games.
Then in 2012-13 he was absolutely destroying the field and takes a Brooks Orpik slap shot to the face with about a month and change left in the season. It literally took the field the rest of the year to catch and pass him (barely) in the scoring race. Again, that cost him a Hart and Ross surely.
Those are the 2 seasons that really stand out as "big" losses when it comes to awards/major bullet points.
While I would certainly put Mario at the top of the "what if" category (probably wouldn't have broke any of the big Gretzky records, but would have at least gotten relatively close), Orr is right there as well. The crazy thing is, most hockey historians put both of them in the top 4 all time, regardless, which speaks to their legacies. And at the end of the day, a lot of folks have Sid 5th best, so again, despite all the missed time, his ability to rebound from some serious medical issues, and keep playing at a very high level for 2 decades just cements his own reputation.