Popular franchises don't keep going up in popularity continuously, they rise and fall. They have a peak. Look at Final Fantasy, wasn't the peak in sales number 7? Also, the number of fans of a franchise doesn't increase in direct ratio to the number of consoles sold. There seems to be a limit, which is normal. I give the large numbers of sales of MGS4 on a small PS3 install base as an example, compared to previous MGS title sales compared to install base numbers.
I can't imagine how Halo could suddenly go from a 10million seller franchise to a 25million seller franchise from one game to the next, it's a kind of utter madness which I've never seen before. Reach will either sell more or less than 3, with little difference either way.
If either franchise is going to be reaching any peaks this generation, it'd be the game in the over saturated market (I refer to first person shooters). Good driving sim games, especially GT are the types of games that appeal to a wider range of age demographics, so for a lot of driving sim fans out there (who we know exist given GT's massive sales in the past) who may or may not own a PS3, a good driving sim game like GT5 is exactly what they're looking for.
There are plenty of games for shooter enthusiasts. Look at the sales of new games emerging into un-tapped markets. Wii Fit, Guitar Hero. Gran Turismo 5 is pretty much tapping into the untapped market of a really good driving sim. Halo has been done.
I don't think Halo Reach (yet another first person shooter) is something people are really yearning for, as good as the game looks. Please don't take any of what I write as inflammatory, I mean it in the best spirit possible as I love both franchises. Halo:CE is one of my all time fav's.
