It's not a better game, it's a completely different type of game.
The original plays like a first-person Metal Gear Solid, in the sense that you are encouraged and generally required to use stealth, Binoc reconnaissance and 'hit and run' attacks to succeed and avoid death.
In Warhead, there is a shift to a more 'run and gun' style of gameplay. You can still use the stealth method, and it yields great results, but the amount of missiles, vehicles and the general turn of the plot means you end up in a lot more open firefights than you would have done in Crysis.
It largely depends on which type of gameplay you enjoy, as to which of the two you'll prefer; however on consoles I suspect a 'run and gun' style of play is probably more popular.