He wouldn't have had much of a career without it. And it helped a lot of other actors/actresses too.

@manfromatlantis : Well Shatner has been reported as one of the few that cared for the series during the Third season and we can thank him for at least some quality according to some people who were around.Also Shatner has also written several books that take place within the Star Trek universe.And Shatner had during the run of the Enterprise series(ENT 2001-2005) contacted the producers with an idea for an episode(two parter) which would be featuring James T Kirk,the producers really liked the idea and Shatner was all game to appear on the show except for the fact the he demanded an absurd fee which was the reason they never made it. So Shatner has never regretted appearing in Star Trek since he owes much of his career to the series.

He also gets a piece of the action. Part of his initial contract specified that he got a share of the residuals. So I'm sure that at least of a part of him damn well likes it.

@sukhisoo I think that he has a love/hate relationship about Star Trek.

He can't regret it that much:

MAY 4, 2017 | BY: TREKMOVIE.COM STAFF 291 COMMENTS SO FAR

Once again, it’s time to talk about whether William Shatner will ever return to his role as Captain James T. Kirk. The notion came up in a new interview with the actor promoting his appearance at this weekend’s Fan Expo in Regina, Saskatchewan, Canada. He was asked by the Regina Leader Post if he would be willing to return:

“I’m perfectly fit and ready to put on some makeup …. The problem I guess is what do you do with an aging captain whose youthful existence is already there?” said Shatner, now 86.

I suspect his desire to return is based on ego. Besides, Captain Kirk died in the Star Trek: Next Generation era timeline so a return would have to be the result of a contrived 'this doesn't make any sense' plot.

@fan_of_films : It would be VERY confusing, especially since considering that he's 50 years older than the current Captain Kirk.

William Shatner said he lived in a car after Star Trek ended. Apparently he was seriously broke.

http://metro.co.uk/2014/02/27/william-shatner-lived-out-of-a-truck-after-star-trek-4324743/

I can't imagine he regrets playing the part (nor returning to the role for the Star Trek movies). I know some people think Shatner is a cheesy over-the-top actor (George Takei said some unkind things about Shatner's acting ability), but to his credit he made Captain Kirk an iconic sci-fi character. Why would he regret that kind of legacy?

@fan_of_films : Yes, I read about that too. I read in a biography of DeForrest Kelley that he and his wife were always worried about Shatner making and losing money all the time. They were also worried about what might happen to Shatner if he got really typecasted as Kirk. They had been good friends with George Reeves, the original tv Superman, and they saw how he got typecasted (Mr. Reeves ended up committing suicide).

@PhelpsFan said:

@fan_of_films : It would be VERY confusing, especially since considering that he's 50 years older than the current Captain Kirk.

They pulled it off with the Spock(s).

@PhelpsFan said:

@fan_of_films : Yes, I read about that too. I read in a biography of DeForrest Kelley that he and his wife were always worried about Shatner making and losing money all the time. They were also worried about what might happen to Shatner if he got really typecasted as Kirk. They had been good friends with George Reeves, the original tv Superman, and they saw how he got typecasted (Mr. Reeves ended up committing suicide).

Allegedly.

@fan_of_films I agree with your post and that Shatner despite his limitations has managed to have an impressive career and have an enduring legacy most movie stars would be jealous of.

@FormerlyKnownAs : Well, that is one theory. I'm also aware of the other theories. But what I was trying to say is that Mr. Kelley and his wife were worried in general about Mr. Shatner.

Is it somehow ironic that, at least so far, Shatner has outlived them all?

@Knixon : Yes, it is.

I think Shatner looks better nowadays than he did 20 years ago ,maybe he found the fountain of youth.