Yeah, they do make for some really nice trophies. I don't have that many right now, but I do have a spare masterball just in case one ever decides to pop up. Right now, my list is a Bibarrel, (best HM slave ever and caught in Diamond), Rapidash (gotten from a really nice person in a trade), and my favorite; a Krabby that was caught in Naranja, which now resides in Black thanks to a little bit of hacking. I used to have a Golbat and a Raticate on Crystal, but that was many years ago before I knew about their significance and some kid tricked me into deleting them by telling me they were extremely dangerous. They will both be missed. I also have the red Gyrados, but I'm not sure if that one counts because it's the one everybody has.
The chance of one appearing in Red and Blue is high if you know the glitch. The real hard part is determining which form appears, which is determined by your name. In all the other games including Black and White, there are equivalents, but you need an Action Replay to find those. I will admit though that it's been a really long time since I did any actual glitching. I can thank Black and White for doing that kind of distracting.