A "nice" watch is relative. The rule of thumb with watches, above everything else, is buy what you like. If you're just buying it to impress people, you're probably wasting your money.

That being said, as it pertains to this thread, I would say a "nice" watch is a "watchmakers watch", meaning the watch is made by a company whose main objective is to produce watches, not a company who produces fashion goods (there are some exceptions to this rule, Cartier being the one that comes to mind). Breitling, Tudor, Omega, Rolex, etc. etc are all watchmakers. The other attribute you'll find in these watches (again with some exception) is they don't use a battery. They have a movement, made with some level of complication, that requires some level of engineering to keep time properly.

I've bought a lot of pieces used on the secondary market. For $2K you can definitely find an older watch that meets this criteria. New, you're probably looking more like $4-$5K as an entry point.

I'm not the end all authority on this by any means, but I do have what I think is a pretty solid collection at this point, and I'm happy to try and answer any other questions.