Yah, it goes like this; the top speed is still what matters the most and what you should look at first (more GHz=better, that hasn't changed) but now an increasing number of emulated systems use multiple cores, like the Namco system** games among others that got an over 20% boost on multi-cores about two years ago (made a massive difference on my rig).
MAME also uses multiple cores when available for other things like dedicated audio and input drivers that are sometimes separate from the base emulated game system driver, which happens even for some 2D games. there's also more room for staying away of where Windows keep things the busiest. The benefits are not always pure game speed performance but could be elsewhere like stability and delay.
Well, at least this is sorta compiled what I've read, you can check the MAME official documentation under the performance chapter, it's made clear that this is a multi-cores emulator, but since they don't list which systems and cases specifically, not even a sampled selection to demonstrate (mamedev's eternal poor documentation and communication-explanation effort) it's expected that many users still stick to several years old information and are kinda perplexed - when not flat out refusing to believe it matters at all - when they read about it.
TL;DR yeah your CPU will be good.