Who is the greatest blitz/speed chess player of all time?

This just isn't true. It's one of the great myths about Tal, but it isn't true. Most of his sacrifices turned out to be unclear, but that doesn't mean they were refuted. 

In the 1970s, Tal had two of the longest unbeaten streaks in history. He was a solid player in later years. His tactics were fantastic.

On the topic of best blitz player though, Petrosian was Tal's equal and Fischer was better than Tal. Still, today's players are better than the players of the past, especially in blitz.

You sure? 

Yes, I'm sure. 

Go through Tal's best games. Sure, you may find an occasional game where his sac was a losing move, but most of his sacs were like the one below. Tal wasn't winning before he played the sacrifice. Computers might recommend other moves, but most of his sacs were within the spectrum of "unclear".

For this particular game, I used lichess to analyse.

Speedy Gonzales

I read that in the book. "how to become a deadly chess tactican" GAMBIT.

From chapter "The Modern Romantics"

"...however many of his combinations and ideas were refuted expecially when computers became too strong..."

I'm not saying Tal was a bad player with luck on his side. Just that "some" (maybe this is more accurate) of his combinations were refuted (or should that be unclear?)

Do you understand that there's a world of difference between playing unclear sacrifices and unsound (refuted) sacrifices?

If Tal had consistently played unsound sacrifices, he would have been crushed by strong positional players. That's what happened to Nezhmetdinov. Compare Averbakh's record against Tal (0-5 with some draws) with Nezhmetdinov's (2-0 with some draws).

Tal was +2700 strength in an era when there were only perhaps two others as strong as that. When he was healthy, he was one of the top 5 players in the world from about 1958 to about 1990.

Shirov, Kasparov, and others have followed in his footsteps. Today's chess players are far better at calculating than players of the past yet Tal still stands as an inspiration to the best players today.

A sacrifice is not really a sacrifice if it is sound.

However the unsound/unclear sacrifices thing is interesting.

How would you describe them?

An unsound sacrifice as one that is easily refuted and can be easily calculated (maybe 5-10 moves ahead?)??

And an unclear sacrifice as something that does give compensation and set some problems not easy to solve even with good calculation (10 - 15 moves maybe?) yet a refutation good move may be found later on that refutes it?
Im confused.

I totally agree.  I think Tal himself is responsible for the myth that his sacrifices were unsound with  his self-deprecating comments.  Tal reveled in and excelled in complex positions whereas most masters seem to prefer more clarity.  Even when a sacrifice loses, it's not necessarily unsound.  

Yes, he once made a comment about a sac he made vs. Averbakh he never would try vs. Korchnoi or Kholmov for example, who were also comfortable in complex positions.

Carlsen