Going back to previous games in a series

With Mass Effect 2 recently taking over the lives of pretty much everyone, it also highlights the point that going back to a prior game in the series can be difficult. Assassin's Creed is another good example of this.  I found today, that going back to CoD4 for a bit of multiplayer was difficult (not that I got pwned, but readjusting to its systems was strange). The differences from Cod4 to MW2 became more obvious and more glaring because of this.
 
My question is this: Do you find it difficult going back to a previous game in a series? 
                               Have there been any instances where you have preferred the previous game?
 
Cheers

I always go back and try and play every game in a series just before a new one comes out. A lot of the time I like older versions, Metal Gear Solid being the best example. The first game was perfect, the rest never really lived up. I also liked the original Half Life better, the second didn't really immerse me enough to truly love it, I haven't played the episodes yet though so that might change. But no I don't really find it hard to go back, I'm not bothered about graphics and different control systems can be learned quickly. As long as there's a good story, I'm good to go.

Total War. My friends and I regularly go back to Rome and Medieval. They're leagues ahead of Empire. Played Shogun for the first time recently, actually; I had fun, despite its age.

I don't have any problem going back to old games. But I can't think of any cases where I thought the older games were superior.

New games usually ruin the older ones for me just because of the graphics and sound.  For example, I don't like Mario Kart 64 anymore because I have Mario Kart Wii.  Also, I used to love the campaign mode of Age of Empires II.  Now I have Age of Empires III.  The campaign mode sucks and I suck at the multiplayer.  Yet, I never play Age of Empires II anymore because 3 is so much prettier. 
 
It's like in that episode of Just Shoot Me where Kevin (Brian Posehn) is fine with eating regular rice until Jack introduces him to risotto.  Afterwards he hates regular rice.

" I don't have any problem going back to old games. But I can't think of any cases where I thought the older games were superior. "

I don't usually have trouble going back to older games if I have played them before in the past. Nostalgia is always the strongest aspect of old games for me. If a game gives me that feeling then I don't care if the graphics and gameplay are dated or not. 
 
Though, if I never experienced the game "back in the day" chances are I won't get anything out of it.

"MGS, Silent Hill, Deus Ex...All had better games earlier on in the series that the sequels didn't live upto. "