I have to admit I've always found a certain charm in black and white. I don't know why. I remember my middle school history teacher used to like to show filmstrips about history, and sometimes dramatizations of historical events (and yes, these were your old fashioned reel to reel filmstrips

). There was always something I liked when he would show a film made in B&W.
Now....Star Trek is best experienced in color, no doubt. While Christopher makes a good point that they made it in such a way as to look good in B&W, it definitely took advantage of color as well. But when I got the very first VHS release of "The Cage" that was a mix of B&W and color footage, I actually found it a bit annoying so I got to the point I'd turn off the color of my TV to watch it all in B&W (as an aside, I always wished they released a version with the unaltered voice of Throne for the Keeper, but I suppose the original soundtrack of his voice might be lost). Watching "The Cage" in B&W did give it a more old school sci-fi feel. "The Cage" always had a different 'feel' to it to begin with, so B&W made it even more so.
And sometimes B&W was the intention. Alfred Hitchcock's Psycho for instance, was made in B&W on purpose. Hitchcock had been making color films for years by then but he felt the B&W would be more effective for a film like Psycho (it probably helped the decision making that Paramount wanted nothing to do with the film and gave him a bare bones budget to do it--though I imagine they were happy with the end result, at least until Universal got the rights

). Probably one of the reasons no one ever even hinted at colorizing it, I mean, could you imagine Psycho in color? As a big horror/slasher film fan it takes a lot to spook me these days, but the B&W does make it just a bit more unsettling, which is what Hitchcock was going for.
On the other hand I saw a colorized version of Night of the Living Dead and I realized it was scarier and more disturbing in B&W. I think Romero would have definitely made that movie in color if he had the budget, but it actually works better in B&W.
Ok, well, I rambled on enough. Part of it for me was probably that growing up we usually had color TV's. Sometimes I'd have to watch a B&W TV but there was always a color TV somewhere in the house so that probably plays into how I see movies and TV's. If I didn't have a choice and only had a B&W TV then I might feel differently.