It's definitely hard to compare to two considering that Sims 2 has a full arsenal of expansions whereas Sims 4 has only just unveiled its first, but the things that Sims 2 introduced (Open for Business and Season especially) where game changing and I remember playing for hours and hours and just having a blast, so 2 definitely has a special place in my heart. That said, I do see Sims 4 taking a similar path. Though very obvious things are missing, I do feel that the gameplay of 4 is a lot closer to 2 than Sims 3 was.