I prefer regenerating health in games because it usually leads to more flow and a faster pace, something you can lose in games where you're constantly looking round for health kits.
And I think that if regenerating health is making a game too easy, thats the fault of that particular game, not regenerating health - i've played a lot of games where my health regenerated but enemies could still murder me on the higher difficulties.
Its not exactly realistic to recover from being shot in 30 seconds, but neither is being able to instantly heal a wound in a second with a first aid kit.
And I think that if regenerating health is making a game too easy, thats the fault of that particular game, not regenerating health - i've played a lot of games where my health regenerated but enemies could still murder me on the higher difficulties.
Its not exactly realistic to recover from being shot in 30 seconds, but neither is being able to instantly heal a wound in a second with a first aid kit.