I voted for the gameplay.
Sims have always had pretty good graphics, even if the older games are a bit dated looking like Sims 2, but they were amazing graphics at the time.
Sims 4 looks super nice with their graphics, but it doesn't have the same gameplay as the older games. Sims 4 you can usually micromanage your Sims, and random events don't really happen.
Don't get me wrong, I do love Sims 4, because I spend a lot of time making Sims, it's just that I can't use mods on my platform, so the game seems fairly lacking on random events that the previous games had.