Experienced Points columnist had it right here when he spoke of pricing and Origin in particular. Origin sucks because it simply offers a handful of AAA EA-only titles at full prices, end of. Steam does not suck because it offers everything from full price (or more expensive!) AAA titles and Day 1 releases from all publishers, indie games, middle-of-the-road fare and sale items.
Here is the thing. A new game comes out at full price of £30. Everyone who eagerly awaited it (and is willing to pay full price) buys it immediately on release and for a month or two after. After this initial period, when it is no longer a new release, the £30 can't necessarily be justified any more. Anyone who wanted it immediately and/or was willing to pay the £30 price tag already has done. So either the game stops selling, or they can lower the price.
The price is lowered to £20 and more people buy it now that it's cheaper, keeping momentum, units selling and people playing. After these sales start to peter out, maybe 6 months-ish after release, it can be said everyone who was willing to buy this game for £20 has done by now and any other sales should be at a lower price point, like £10, again attracting new customers who a) wouldn't have otherwise played it b) might have otherwise pirated it c) were never going to buy it for £20 or even £30.
Borderlands GOTY is on sale at Amazon right now for less than the cost of two of its four DLCs on Steam alone. Is Amazon devaluing Gearbox's IP? Steam is over-valuing it I should say. Was a time when games several years old were a fraction of their release price. Now publishers, particularly Activision rarely drop prices.