I was very disappointed in 4 when it came out and it took me 8 months to go back to 3. But I've been playing 3 since, and having a blast. It's such a nice feeling to be able to add mods and cc without dealing with patches!
I opened 4 and played in an hour or two last week, which was the first time I'd played in over two months. Collected two sugar skulls and then had to quit for the evening. And I've really had no desire to go back to it since, and have been playing TS3 instead.
I'm rather in the same boat as @Cynna; I need so many mods to enjoy it but keeping them updated is too much of a pain. Plus I really just haven't found a way to play it that's fun and engaging for me. I'm sure I'll still play it every now and then, especially after its finished and mods won't be such an issue, but I don't think it's ever going to become my main Sims game.