I want to know what your definition of "better" is when determining if a region is better than others. Is it depth? Overall skill level? Or just how good the top teams are?
Imo it's a mix of that.
If you want to consider all time, I think trophies is the obvious metric.
If you want to talk about rn, I think there are many metrics that need to be used, together.
Ranked for importance:
1) strength of the top teams
2) strength of the top players
3) competitiveness of the league
4) strength of the middle teams
5) strength of the bottom teams
Average placement of a region matters more, because if you look at it, sure EMEA has a lot of trophies, but the thing about EMEA is, they always have that one team that's so good that they win the entire event. That doesn't mean the region as a whole is good. In Masters Tokyo, the average placement for Americas teams was 4.66, 6.33 for Pacific and 7 for EMEA. It gets even worse for EMEA when you remove FNC.
EMEA has the most trophies, sure. But that doesn't mean they're the undisputed "best region" in Valorant. They're just super top heavy.
Take a look in VCT EMEA as well. KC, KOI, TH and BBL are literally so bad compared to the 5th and 6th best team in EMEA.