There are about 7 seasons since the 2005 relaunch. I'm gonna warn you, the show is--inconsistent. It features some of the best episodes of television period and other episodes are absolute crap. In my opinion the show gets way better at season 5 but I was definitely a fan before that point. If you have the patience to watch bad episodes start at the begining. Before you start that, maybe watch an episode called 'blink'. That's a good standalone episode that will give you an idea of how good the show can be. Season 1 has quite a few bad episodes but it has some great ones like dalek, fathers's day, The Doctor dances/the empty child and it's the only season featuring the amazing ninth Doctot. However, there are three episodes in season one so bad I'm tempted to advise you to skip them completely--aliens in london, world war 3, and boom town. If you've watched 'blink'(from season 3) and all of season one and you're not interested to see anymore then it's probably not for you.