Yes, it's a long topic, I know...

The question that I'm asking is whether or not the sequel of a game that had mediocre launches (but strong legs) would end up having the same fate as the first game in terms of initial sales, OR would the sequel typically do much better in terms of launch sales due to the point that the first installment slowly built a name for itself?

Two recent games that I find off the top of my head that fits this mold is Uncharted and Resistance.

According to VGchartz. Resistance sold 242,258 on it's launch days (obviously not on the same day) and Uncharted sold 136,691 on it's opening week. While at first both games could be considered flops, in the end RFOM ended up with almost 3million and Uncharted 1.7 million because of great legs, good reviews, bundles, etc. Should we be expecting a monumental increase in launch sales or around the same?

I think both of their sequels will have large launches, mostly because they will be even more hyped. Uncharted in particular will benefit because it spread mostly due to word of mouth, and so because people were impressed with it, they will jump straight onto the Uncharted 2 bandwagon at launch

They have built a name, and the sequels should perform a lot better than the predecessors.
Just look at Guitar Hero. The first one sold horribly at the beginning and didn't reach a million till the second one launched. Now the third has sold more than 9 millions platforms combined

So we're now expecting those games (that didn't have great launches before) to have much better launch sales. If that's the case, then does that mean they won't have the large sales they've gotten via legs?

Should have a larger launch as there are many people who bought the titles, enjoyed them and are waiting for more.

Ya but Resistance launched with PS3 which had 0 install base. So its sales are Very good.

This should be broken down by company (Sony, MS, Nint.) and have a few sales compared.

It's not uncommon for a sequel to have a better launch or lifetime.

Part of their low launch is due to them being released early in a console's life which will automatically reduce their opening weak. It would be almost impossible for those games to have a lower launch now given that the console has sold far more.

It's also extremely common for sequels to be more frontloaded than the original. This happens with movies, and to a lesser extent books, as well.

What would be more interesting is considering games that did legitimately debut low, such as Viva Pinata, and seeing how the sequel launches.

I would say that sequels generally become more frontloaded in their sales. A lot of sequels also tend to sell less than their predecessors. Of course, there are always exceptions.

I don't have any actual data to back this up, but if you looked in the game database, I'm sure you could find some.

Very interesting question. I may look into this further.