is that what you meant? because FF7 sold more than FF8

but to answer the question yest I do think FF8 is better than 7 (its actually my favorite 3d FF game).

Not at all . It´s like rock/pop music, there are great bands with great records that don´t sell good enought. Some fantastic games flop and some bad or regular games hit the charts because of good marketing or famous franchising.
It´s very possible that Infamous and Heavy Rain gonna be quality games without topping the charts.

Carnival Games for Wii sold as much as Bioshock for 360 and they are both from the same developer!

If a game doesnt sell well doesnt mean that game is bad. But if a game sells well means there is at least something to it that makes it worth the price.

Bad games don't sell in the category they target. Good games may not sell. So a game that sells has quality. What we value as quality though can vary to different people.

I would love to see a new 2d brawler that has 4 player co-op than a 3d brawler like mad world with no co-op. Even if the game was more bland, and ugly I would value it more.

Edit: as for Imagine series. Well as I said in my first sentance Bad games don't sell to the target category. To be clear the Imagine series have NO COMPITION and thus they are the category. Remember put out products that don't exist and it will sell. Their really isn't much in the way of Baby tamagotchi for the DS, so for girls that wan't a Baby simulator it's the only option. The fact that the game sold 2+m only means that a market actually exists for this type of game. If other companies are blind to take advantage of it then it's their loss. Consumers will just have to put up with crap game design until Ubisoft has compition.

Of course not

Of course not!

I don't understand this point, that is the foundation of what you said next.

Discounting rentals and demos, that are a small minority of cases, people buy a game first and form an opinion about it next. What they have before playing a game can't even be called an opinion. It's an attitude, inclination or belief driven by knowledge of genre, authors, reviews, theme, imagery (or lack of such knowledge) but also by marketing.

We can surely name a lot of games that sold very badly, but highly regarded by almost all those who played them. Same as some movies or some books, really.

If you think Sales=quality, than I feel sorry for you. I mean, in every industry there's something called luck, some games catch on, and some games don't, even if it's quality.