This is correct. There's a difference between those who have good moments and bad moments vs someone that comes on the screen then leaves and leaves not much of an impression on the scene. That's what I've seen out of Ross, at least.
This is pretty much why Ross should be somewhere in the lower half. Perhaps tied for last with Rachel, which would make my ranking:
Chandler > Joey > Phoebe > Monica > Ross = Rachel
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"Coinflip is sacred."