I wasn't speaking down to you, but rather the people that would assert Morrowind is some kind of incredible game just because they haven't played anything else.
As for popular opinion, I think it's been pretty much made clear that it really has little to no impact on which game is better. Look at the OP, he has games such as HoMMII on his list, most people in all likelihood have only played HoMMIII or its sequels.
EDIT: Quoting is messed up.

How do you know what other games people may have played?
It sounds like you're trying to put a purely subjective concept (which game is better) into a purely objective framework. There is no way to measure how good a game is, all there is is opinion. If the popular opinion is different from yours, it doesn't mean the popular opinion is wrong, nor that yours is. They're opinions. However, there's something to be said for the viewpoint that a game that many people like by definition has to be good. It has to somehow connect with all those people in order for them to like it. If it doesn't connect with you, it doesn't mean that it's a bad game, just that it's not a game for you.
As for most people having played only HOMM3 or later, that's basically a matter of age. I'm 31, and I've been gaming since around 1987, so I've played lots of really old games. And I'm not the oldest member here, not by far.

I'd say this is too general as a rule, and seems to ignore many games.
Personal list of second parts not the best of its series (but not necessarily bad):
- Prince of Persia 2
- Prince of Persia: Two Thrones
- Deus Ex 2
- System shock 2 (yeah, it is great, but for me the first one is THE ONE)
- Half-Life 2
- Half-Life 2: Episode 2 (even worse than Episode 1 =) )
- Homeworld 2
- Chrono Cross
- The Beast Within: A Gabriel Knight Mistery (wonderful game, but not better than Sins of the Fathers)
- Max Payne 2
- Rick Dangerous 2
Personal list of excellent second parts:
- Riven: The Sequel to Myst (my favourite game ever, followed by Myst itself)
- The Settlers 2
- Seiken Densetsu 2 (Secret of Mana)
- Phantasy Star II
- We Love Katamari (Minna Daisuki Katamari Damacy)
- Persona 2: Innocent Sin/Eternal Punishment
- Master of Orion 2
Both lists are incomplete, but they should prove (or not) that:
1- I have good taste (for some people)
2- I have terrible taste (for many more)
3- Second parts can be better or worse, no matter how good was the first one, in a 50-50 proportion.
4- From the third instalment on, things usually go down in very bad ways.

This rule can also be reversed where first games were better than the second one.
Super Mario Brothers 2?
(Although, 3 was the pinnacle)

I would like to disagree with you in a non-flamewar kind of way. Super Mario World was the pinnacle. Thank you.

I like your style :-P

How do you that? The only objective thing you can measure in a game's goodness is popularity. Nothing more nothing less. Yeah it's a pain in the ass but it's true. In my opinion Titanic was rubbish but it is and will be the highest grossing movie in the history for a long time (maybe Avatar, fingers crossed) so maybe it is really that good just i can't understand it. :-). And of course i am pretty sure you haven't played all RPGs of all time so how do you know isn't there one which is much better then anything you've ever played? That's the same with Morrowind lovers. How could you say that they have never played HoMMII? Maybe some of them did, but maybe just maybe that game wasn't for them.

Perhaps the most important thing to note about popularity is that the sales figures for games these days are well reported and that more people are gamers than 10-20 years ago.
This means that Fallout 3 for example may have sold in the millions, whereas Fallout 1 sold less than 1 million, perhaps a lot less than that (before GoG). Therefore, you can extrapolate that most of the people who have played Fallout 3 have never played the original.

Blood 2, worst sequel ever.
Stalker: Clear Sky is also worse than first one.

I don't see why. They are the same instead. Both are pretty damn good games but it's a shame that in ~6 years they wasn't able to write a freakin' main story for either of them. But it's the usual nowadays. isn't it?.

What is this "story" you speak of?

surely these days with the success of things like world of warcraft, all you need in a game is endless repetitive combat and plenty of fetch quests.

Clear Sky is an unfinished game. Yeah, I know first one has also some problems but Clear Sky's problems are bigger than the first one. They released 8 patch for the game but nothing has solved in game. GSC is trying to make multiplayer better with these patches but no one is playing Stalker's multiplayer modes. They must repair sp first, also I bought the game from Steam and game has 5 time activation limits. Yes, stupid DRM.

Sorry, I don't understand your question. :-\