Just to sound Nostalgic, Morrowind really got the Speech Skill down correctly. Other than Taunt, which was just a way to murder someone without penalty, the skill really had impact in that series in every conversation.
I agree, it's the only one of the series to get it half decent, Arena didn't have it and daggerfall's was kinda borked. Oblivion's was way too silly, bribing was too abusable and it still had little impact. My only issue with Morrowind was the tendency for the threshold to always be 70 disposition, that and it could have done with a few more ways to increase disposition - I never really used intimidate as it seemed less successful than admire. Still, I'm not saying Morrowind's system was amazing, just better than the others. On bribes MW was better because it could fail, but 1000 gold rarely did so once you started swimming in money everyone loved you.
The fallouts are good but heavily pre-scripted, not much of a dynamic element to them. NVs better than FO3 but still had the flaw of showing in advance the exact skill, I'd maybe have merged the two, saying "At least X, then percentage up to Y, then always successful" and then not shown the numbers.
Skyrim's system isn't actually bad, when they say "behind the scenes" they actually seem to be alluding to the unused potential set up by the system (e.g. The relationship data in the CK)