Foregone conclusion. Keeping in mind it's comparing apples and oranges. 99 had to play with a goon on his line his entire career. 99 also played during the hooking/slashing era. And had 99 shot more than passing, Ovi wouldn't even come close. Say Gretzky shot on 500 of his passes instead. Likely would be another 100 goals at least.
"99 had to play with a goon on his line his entire career. 99 also played during the hooking/slashing era"
-> Considering both of these things, scoring goals was still statistically 30-40% easier in Gretzky's era than in Ovechkins. Therefore the lack of defensive systems, small goalie pads, worse goalie positioning etc. therefore was a significantly larger advantage for Gretzky than any of these couple disadvantages you mentioned.
"And had 99 shot more than passing, Ovi wouldn't even come close."
-> This assumes two things: One being that Ovechkin hogs the puck and shoots when he should have passed - that is incorrect, as anyone who has watched Ovi play knows that he passes A LOT, and it just happens that Ovi doesn't play with great goal scorers. Ovechkin will routinely pass on 2-on-1's just because he thinks his teammate has a better positioning. Secondly - it assumes that Gretzky wasn't always making the best decision with the puck - he was (he's the best player of all-time). If he had a chance to shoot and it was the best option for his team to score, he did (Gretz lead the league in shots 4 times, and is 7th all time for forwards)
"Say Gretzky shot on 500 of his passes instead. Likely would be another 100 goals at least."
-> So you think if he took 500 extra passes (at times where it wasn't the best play to make - ie. he just forced a shot that wasn't the best choice for his team), he'd score at least on 20% of them? His career shooting % is 17.6% - and like I said, he's the best player of all-time, if he truly was that great, he wouldn't have passed up on shots that had a high scoring probability just to pass it. Also worth noting that passing and assists can be generated from soooo many places that are not goalscoring opportunities on the ice.