Which Sims game: 2 or 3?

Hello! My birthday is coming up (July 1st) and I'm getting birthday money...i currently have the Sims 2 and i love it and i like everything about it...right now i have seasons , pets , nightlife , home and garden , celebration stuff , and family fun expansion packs the graphics on Sims 2 are really nice and they look realistic , but on the other hand there's the Sims 3...so I'm wondering , should i continue my Sims 2 collection or go out on my birthday and purchase the Sims 3(is the Sims 3 really worth it? please answer I really don't know what to do...