About Mass Effect:
The hype for Mass Effect is beyond the typical WRPG crowd. The game incorporates heavy shooter action. Moreso than KOTOR ever had. Because of this, and the fact it's the spiritual sequal to KOTOR, I think it will garner sales from both sides of the spectrum. I remember just about the same level of anticipation for this, as I did for Gears of War last year, so I'm posting similar numbers.
Initially, I figured it'd cater more toward the KOTOR-only crowd (that is, to sell 1.5m in the US), but it just seems hype is way beyond that. KOTOR was a shoe-in for RPG GOTY or near that. Mass Effect has a chance to win GOTY outright. Because of this, I think it's going to enjoy great, great legs. As stated, Oblivion wasn't exclusive, which hurt it kinda. But moreso than that, Oblivion was a near-launch game, and still sells today. Once it's GOTY edition comes out, Oblivion could wind up with near 2m units sold in the US (Morrowind's GOTY sold insanely well, and I do believe it was one of the top-selling platinum games in the history of the black Box.)....So I believe it'll do somewhere in the middle of Gears of War and Oblivion.
It's the same reason I think Fallout 3 next year can do ~2m on the X360, and still sell near 5m copies on other systems. Us Americans and Europeans love us a good WRPG. And again, Oblivion continues to sell. Two Worlds will be a great barometer of the market of WRPGs for Mass Effect, but I think Halo3 will have more of an impact, as once H3 wears off, the next logical game for "those" kinds of people will be GTAIV and/or ME.
I don't think 750,000 for Lost Odyssey is too low, or too high. FFXII only has sold 1.6m copies in the US, despite its great pedigree. The issue with BD is it's kind of a step-child of both Dragon Quest and Final Fantasy, and not entirely DQ-esuqe. The advantage it has is that it's "from the creator of final fantasy", which might help, while Lost Odyssey has the whole "Final Fantasy Killer" name behind it.
But again, everyone, even real low numbers are just as valid. Having no real precident for actually decent JRPGs on the X360, and only Oblivion to go off of for major WRPGs is a diffuclt task to figure out. But with Oblivion selling ~5k copies a week, only down from ~7.5k from CHRISTMAS, shows that WRPGs are a very, very strong market on the X360. IMO, a game like Oblivion selling THAT strongly is showing the X360 might be catering to a different crowd, and the RPGs could vastly benefit from it. If not, and its just the shooter crowd, then Mass Effect could top 3m in the US alone :)