I've only played a few other MMOs before but none of them had this problem.
LOTRO - There was a brief period when the game first launched it had RMT, but then Turbine put in rules to stop it and it never happened again.
DDO - Didn't play when it was first launched, so I don't know if it had a similar brief period of RMT vulnerability, but there was no RMT spam there by the time I started playing.
(Guild Wars - Well, that was a long time ago, so maybe RMT just wasn't as big of a thing then as it is now.)
So far, from my experience, RMT is 1 for 4, with FFXIV being the 1. Anyone saying it can't be stopped doesn't know what they're talking about. It can be stopped, and has been in other games. (And there have already been plenty of other threads describing how.)
