That's a difficult question, it depends what you class as greatest. Do you mean the most iconic, best performing of its time or currently best performing.
If you mean currently best performing then you run into the issue that we just don't know. As far as I'm aware nobody has put the best frames side be side in a testing situation. Then you have the issue of what do you class greatness on? How are? How stiff?
Imo the two main contenders are the Look R96 and BT Edge. The look is used by many teams although that is due to many teams being sponsored but it is a very fast frame and the BT because it has been the choice of bike for many sprinters when their sponsored bike isn't up to the task. Such as the kiwis before they moved onto their current avanti frames, the sprinters would use blacked out BT's.
Also BT is Australian, which automatically makes them better.
This isn't taking into account the "money can't buy" frames like the German FES frames or the Cervelo T5. They're developed for particular teams and not sold to the public. Though the t5 may someday be released to the public.
Also a shout out to the Koga Kimera, a reasonably old design (new version has been teased for the last few years) but the Dutch sprint team use them and they're **** hot atm. So can't be too far off the mark.
If you are talking pursuiting or mass start races then I'd be inclined to say the new Argon 18 frame, seems to be getting chosen by more and more teams, including the likes of team hubb wattbike who seem to be very into what eqipment they use.
