No lady of Star Trek was hotter than T'Pol of "Enterprise" but many were close.
I loved "Enterprise" as a separate show, but I am sure trekkies will agree it didn't really fit well as a prequel to TOS.
For a best episode, I have to say that episodes of TNG were generally more mentally stimulating than most. I enjoyed the introduction of the Borg and the episodes that dealt with Data and his "family." Also, Q episodes were pretty good. But the best of all, in my opinion, was "SHIP IN A BOTTLE" where holographic Moriarty (of Sherlock Holmes fame, but recreated by Enterprise computer as an adversary for Data) is powered up for a second chance to free himself from the holodeck.
A close second is an episode of TNG called "The Measure of a Man" which is highly issue-oriented, the issue being whether building a race of Data-like androids would be building slaves by trying to decide if Data is property of Star Fleet or an independent lifeform.