It's hard to recommend this originally unaired first pilot (later incorporated into "The Menagerie Parts 1 & 2"), because technically it does not exist within the canon. If Christopher Pike hadn't showed up in "Menagerie," he wouldn't exist (until the the movie reboot) in the franchise, much as the even more unofficial Robert April doesn't (although the captain featured in Gene Roddenberry's original pitch does show up in The Animated Series, which itself is always considered quasi-canon). This also technically counts (and doesn't) as the first appearance of Spock, the only holdover between first and second ("Where No Man Has Gone Before") pilots (even though the studio specifically asked for him to be eliminated!).
Anyway, so the story is exactly the same as later featured in "Menagerie." Pike becomes a prisoner of the reality-warping Talosians, and his only companion is the mysterious Vina (who also gives us our first alluring glimpse of the Orions). Pike eventually figures out what's going on and bullies his way to victory against these first of all theoretically-superior-but-really-morally-inferior aliens.
I wouldn't have minded had this become Star Trek. Not very theoretically, nothing that Star Trek ultimately became (except for Spock) would have happened, of course. Pike actor Jeffrey Hunter was dead by the end of the '60s, for instance (died a few months shy of the first moon landing, in fact). But this was not such a bad show.
The character of Dr. Boyce might have been interesting. He wasn't just the chief medical officer (and close friend of Pike), but also ship's bartender, leading to such characters later in the franchise as Guinan, Vic Fontaine, and even Neelix (not to mention the never-officially-seen Chef from Enterprise). Number One, portrayed by Majel Barrett, would have made history simply being a woman. Pike himself would have been more like the Kirk of the early movies (Motion Picture, Wrath of Khan, to be precise), wondering about the future of his career, than the headstrong Kirk we know and love. NBC rejected "The Cage" because it was too cerebral, and it's easy to see that Pike was a major reason why the pilot was the way it was.
Spock? He's a little different here, not quite the Vulcan we know (but still portrayed by Leonard Nimoy, for the record). But hey, Spock's still, already, of course he is, present!
On its own merit, as well as for curiosity's sake, I recommend this episode, in its original form. But you can stand to live with it, for any number of reasons. For completists of the series, perhaps.
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Memory Alpha summary