Both dual-core i5s and i7s have Hyper-Threading
Hyper-Threading actually doesn't work like that. The two threads for each core are not a physical and virtual thread like some people may claim. They are both virtual threads and they share the core's resources. Hyper-Threading doesn't double performance because the core only has so much resources and at any given time, one of the threads will usually use most of them. At best, Hyper-Threading gives a roughly 30% performance boost and dual-core models often get around there in their boost over similar non-Hyper-Threaded models in modern DX11 games.
Games are written to take advantage of as many threads as they can which usually means four threads for most current DX11 games. The games don't know that there is a difference between physical cores and virtual threads because it just sees things as threads; it is the OS that knows the distinction and schedules stuff appropriately.
As time goes on, we get code the games to better take advantage of modern CPUs. Since we have more threads available to many CPUs then we did several years ago (six and eight threaded CPUs are much more popular than they were say three years ago, especially before Nehalem/Westmere when they were almost unheard of), we have been coding games to be capable of making use of those additional threads more effectively. Compare a game such as Skyrim that is still not too old, but an older DX9 game IRC, to a game such as Crysis 3. Crysis 3 will easily scale across as many as eight threads (perhaps more, I've never seen a test done on a CPU with more threads) whereas Skyrim will probably not scale across more than two threads very effectively.
Both of the CPUs that you're talking about have four threads from two cores with Hper-Threading, so it doesn't really make a difference in this for which way you go.
The games that you mentioned do not scale well across more than one or two threads, so I wouldn't worry about needing more than a dual-core CPU anyway.
Also, Cry engine games are by far not the only ones that scale well across six to eight threads. BF3, for example, doesn't use it IIRC and I know for a fact that it's multi-player mode can very effectively use eight-core CPUs such as AMD's FX-8350 and in it, the quad-core i7s also show their advantage over the similar quad-core i5s. I know of several other non-Cry engine games that can utilize six to eight threads too.