As excellent as Sanchez is both of those two would be quite an upgrade on him. Alexis numbers at Arsenal are ridiculous considering he has played majority of the game as a winger and it's close to 0.50 goals per game but Griezmann numbers are even more bonkers at Atletico it's at 0.62 goals per game and that's not even taking into account how defensive Atletico can be at times compared to Arsenal who play expansive football.
I don't even want to get started about Bale and it's laughable that you put Hazard above Sanchez (who is put above Bale!), you'd be laughed out of anywhere if you suggested that Eden Hazard is better than Gareth Bale. Bale has become integral to a Real Madrid side which has been dominated by Ronaldo, that in itself is an achievement especially when compared to the fact Sanchez couldn't hold a place in the side when he played alongside Messi at Barcelona. I don't see Bale moving on from Madrid anytime soon but he'd instantly be best player if he came back to Premier League.