I would tend to agree with Ducimus and Sailor Steve.
I'm not sure 'immersion' neatly fits into a one-size-fits-all category. For my part I would define 'gameplay' as the ease (or lack of same) by which the player can settle into, understand the intended concept and enjoy the game. 'Immersion' is the individual player's emotional? connection while playing the game.
In that vein I would venture that SH3 w/GWX provides more immersion for me in that I can get caught up in the stress of evading a serious DC attack or trying to get in position to attack a convoy. Ergo the gameplay between SH3 and SH4 is quite similar but the immersion factor is different. I still enjoy both but for different reasons.
By the same token, take a game such as "B17, the Mighty Eighth". The gameplay can vary depending on how much of the bomber you want to control. I, personally, enjoy the immersion of playing the bombardier and gunners and taking care of the crew without actually flying the bomber (which can be quite involved in itself). It can still be quite immersive despite the lack of current day graphics and 3-D enhancements/technology.
I would suggest that the games that provide good gameplay and/or immersion are still being played by many of us. Which games they are is due to personal taste and personal opinions on what constitutes gameplay or immersion. The result: a satisfied customer/gamer, which, to us, is the bottom line but to UBI it's probably more quantity than quality hence the dire need for modders. Games that do NOT provide good gameplay and/or good immersion are quickly dumped and forgotten which, again, is a personal choice as I'm sure there are many people who have dumped SH3 and SH4 simply because they didn't like the gameplay or were not satisfied with the immersion.
I digress. Apologies.
