for single player games I usually wait till a price drop because it will be just as fun to play day 1 as it will be 3 months later. I also wait for more niche titles that don't sell too well because they will likely go down quickly.

I don't wait for games that are big blockbusters mainly played online because my friends will probably be getting them day 1 and if I get the game a few months late they might have gotten bored with it.

Um, because I can and I choose to? The price of freedom I suppose lol

A few reasons why I pre-order/buy day one.

1) Pre-Order bonuses via ingame items and what not.

2) Amazon Credit - Amazon offers $10-$20 for most games in game credit for pre-ordering. For example I'm getting $10 off Super Street Fighter IV and Halo Reach. I doubt either of those will be on sale for $30/$40 respectively in their first month.

3) Limited Editions - Ubisoft made all Prince of Persia games limited editions with pre-order. Some games like Mass Effect 2 LE we worth it because they became out of print and more expensive to buy afterwards. You gota becareful with this one though because some LE's are worth way less like the Bioshock 2 Limited Editions which went on sale for half the price a month later.

4) Rarity - I don't foresee Samurai Shodown Sen being a very well produced game, same with Deadly Premonition so I pre-ordered those. Most games (95% or more according to pricecharts) end up selling for less then the retail cost so your really taking a risk here, but some games end up being rare/valuable so I pre-order them.

5) I need the game in the first week - Pretty self explanatory. I don't want to wait long to get my hands on Halo Reach or Ghost Recon 3, but some people are willing to wait for a price drop. More power to them I suppose.

I got a $17 store credit at Gamestop and Super Street Fighter 4 comes out on Tuesday. Why WOULDN'T I buy it on the first day? I only have to spend $23!!

I don't pre order because it's to expensive over here in germany but I have to say that I missed some good games because I'm not that hyped for them anymore
I order my games from UK because it is cheaper , just earlier this day I was at games store and they realy sell batman arkham asylum for 66$ and that wasn't the GOTY edition
god of war costs 90$
so I think you see why I don't buy games first day and I don't buy games at stores