As a Base Game alone (not including patches/expansions, etc) Sims 3 was able to maintain my interest far more than Sims However (bugs/glitches aside), TS4 runs far much better for me than TS3 did.
I like them both for different reasons. With TS3 and all of it's expansions, open-world, color wheel & casT, it's hard to compare both games, seeing as how things have changed. Perhaps with future TS4 EP's, GP's, etc., I will be as psyched to play as much as I had with TS3.
For me, Outdoor Retreat GP was able to bring me back to playing & able to enjoy the game more. It had been weeks and weeks since I last played TS4, due to a growing lack of interest. The new GP re-kindled my fun and entertainment. I have a feeling future ad-dons to the game will do the same as it had done with TS3.