It is, BW has a great story and BW2 has a lot of awesome post game content, It would be a waste not to experience either. Don't worry about repetitiveness because BW2 adds a ton of new cities, spices up some of the already existing ones, and completely changes up the order in which you go trough them, in addition to giving you a crapload of great pokemon early on to use on your team (you can get a Lucario really early on for example).
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The sequels are better, but I think BW are good too. It should help you with the story to play BW first, but I think everything is pretty well explained in BW2 concerning what happened in the first games.