Kirk's original characterization was essentially indistinguishable from Pike's: serious, driven, weighed down by the burdens of command, too focused on his work to have time for women.
"Too focused on his work to have time for women"?
What about Areel Shaw, Dr. Helen Noel, "Ruth", and "the little blonde lab technician I aimed at you"? And let's not even mention those tear-jerker flings with Edith Keeler or Miri.
Areel was someone Kirk was involved with nearly five years earlier, before he became a starship captain. Ruth and the lab tech were from his Academy days. I'm talking about his time as a starship captain. It was clearly established that he was "married to his ship," which prevented him from pursuing relationships.
Helen is a classic example. A lot of people think they were actually involved, but they're forgetting what really happened in the episode. In reality, as we were unambiguously told, Kirk and Helen only danced and flirted a bit at a Christmas party, and Kirk was uncomfortable to be reminded of that. Kirk had to be brainwashed into believing he was in love with Helen, and even so, all it took was a simple reminder of his duty to enable him to overcome that powerful brainwashing and go right back to treating her as merely a crewmate -- even quite callously sending her into a potentially lethal situation.
As for Miri, Kirk certainly didn't show any actual romantic interest in her; he was just being friendly and she misconstrued. If anything, that episode underlines Kirk's duty-over-romance characterization, as it reveals that Janice Rand has been trying to get his attention for months and he won't even look at her legs.
And look at "Mudd's Women." Remember, I'm talking about how Kirk was characterized
at the beginning of the series, before that characterization was affected by Shatner's personality and network pressure. In "Mudd's," Kirk is the only male crewmember other than Spock who isn't going gaga over the women. While everyone else is openly drooling, Kirk seems more annoyed by their presence than anything else; he's aware of their attractiveness but reacts to it as a distraction and doesn't let it break his focus. Eve tries to seduce him and gets nowhere.
As for Edith, first of all, that's from the end of the season, so it isn't really apposite to my point. But even so, it was presented as an exceptional circumstance. Kirk wasn't on the ship; he was living in Edith's world for an unspecified amount of time, possibly weeks. So he wasn't really in a command situation. The defining dilemma of the character as originally conceived was duty vs. personal life, marriage to his ship vs. his longing for love and commitment (see his monologue in "The Naked Time"). Here, the ship was out of play. And it wasn't just a fling; he fell deeply in love, in spite of himself.
If you look at the first season overall, all of Kirk's involvements with women were either: a) from his younger days (Ruth, Areel); b) initiated by the women without success (Eve, Rand, Miri); c) calculating ploys on Kirk's part to achieve his goals (Lenore, Andrea); or d) the result of Kirk not being in his right mind (Rand in "Enemy Within," Helen). And many times, particularly in the earliest episodes which are the focus of my point, Kirk is detached and levelheaded while other characters are seduced by feminine wiles ("Mudd's Women," "The Man Trap," "This Side of Paradise"). We began to see the first hint of "Kirk as womanizer" in "The Menagerie" with the starbase yeoman, but Edith Keeler is the first woman that Kirk enters a genuine romantic relationship with during his tenure as captain. And it didn't happen until a year into the series.
On a serious note, I've read people in this forum suppose that if Jeffrey Hunter had continued on as Captain Pike in TOS, the series would've been significantly different. Given the discussion here from the opposite angle, maybe Pike would've delivered the same kind of presence as Shatner's first-season Kirk.
It's possible Hunter would've been willing to try to develop his character in the same way, but I'm not sure he would've had the same charisma as Shatner.
