Gretzky scored his 500th goal in his 8th season. Based on hockey-reference's adjustments, these are Gretzky's adjusted goals for his first eight seasons:
Gretzky: 1) 43, 2) 42, 3) 68, 4) 57, 5) 69, 6) 58, 7) 41, 8) 52
Total: 430
For Ovechkin the results are as follows:
Ovechkin: 1) 52, 2) 48, 3) 72, 4) 59, 5) 55, 6) 35, 7) 43, 8) 62
Total: 426
Gretzky is a little better, but the adjustments aren't perfect for different reasons and one can make arguments in favor of one or the other. Also Ovechkin's 8th season is strike shortened, but the adjustment assumes a full 82-game schedule.
Nevertheless for seasons 9 and beyond, Ovechkin's scoring is much better.