Voyager's my favourite! :) But, it's also the only one I've really ever seen.
My father loved Star Trek back in the 80's, but the one episode I recall watching was boring and had nothing on Star Wars, so I never really got into it until Voyager was on day-time TV and there was nothing else to watch, thus drawing me in. Now I own every season of it and apparently need to watch Deep Space 9 too.