This is very relative, but if I had to put my money on of 'em, I'd bet on the second quarter.
- First quarter is completely "lost", Heavy Rain and God of War will make PS3's sales boost so.. if you vote for 1st quarter, I must say, WHAT THE F IS WRONG WITH YOU LOL
- Third Quarter/Fourth Quarter, there is Halo Reach and Fable. But who will buy Reach? The millions of people who bought Halo 3. And those already have one 360, so I honestly don't see it being a system seller. Surely will boost the 360's sales, but nothing like Halo 3. IF, MS reduces the price by that time, and not on the second quarter like I predict, and heavily bundles it, then perhaps, but Halo Reach by itself won't give the victory to MS, specially because it will have to face the almighty GT5, case this one doesn't get delayed again. Natal and the Arc/Gem/Dildo... won't sell much if the PS360 don't get a price cut, so I don't consider 'em relevant. However, I can be badly wrong.
-> Second Quarter, I think Microsoft will cut the Xbox's price in April or May (Alan Wake), mainly because of what God of War will do to PS3's sales during March and April. In the other two months (May and June), the 360 will have plenty of time to catch the PS3.