Bale, Giggs... not sure who to put next — Valencia, Overmars, Blokhin, Mbappé, Walker, there are so many!
Players generally got a bit faster these days so on one hand you get more contemporary candidates but on the other one the likes of Blokhin in the 1970's, Boniek in the 1980's or even young Giggs in the 1990's visually stood out even more against (on average) a bit slower opposition.
Put preference on attacking players as I like to judge player's speed with the ball at their feet instead of a straight off-the-ball sprint. Luis Ronaldo has to be the most devastating fast player ever even though I'm not sure if he's going to beat Bale (or a few others) in a straight race.