Bruce Lee would beat a lot of UFC fighters in the striking department. He had speed and power that is unmatched even today. He is pound for pound the strongest person who has ever lived in my opinion. I'm not sure how he would do against great wrestlers though.
Lee's phenomenal fitness meant he was capable of performing many exceptional physical feats. The following list includes some of the physical feats of which, according to author John Little, Lee was capable:
Lee's striking speed from three feet with his hands down by his side reached five hundredths of a second.
Lee could take in one arm a 75 lb barbell from a standing position with the barbell held flush against his chest and slowly stick his arms out locking them, holding the barbell there for several seconds.
In a speed demonstration, Lee could snatch a dime off a person's open palm before they could close it, and leave a penny behind.
Lee performed one-hand push-ups using only the thumb and index finger.
Lee performed 50 reps of one-arm chin-ups.
Lee could cause a 300-lb (136.08 kg) bag to fly towards and thump the ceiling with a sidekick.
Also, according to the Intercepting Fist DVD, Lee would hold an elevated v-sit position for 30 minutes or longer.