I find Tony Jaa amazing to watch - good to see Muay Boran used in such a physical and gymnastic way.
However, Bruce Lee is a legend for a reason. His understanding of a variety of martial arts, combined with his immense speed, raw power and awesome Do form approach coupled with a Jutsu form effectiveness leaves him second to none imo.
Watching Lee in action makes me realise that, as eye pleasing as more modern day artists are, nothing compares to things like this:
Bruce Lee > Donnie Yen > Jackie Chan > everyone else