There's simply no way you can max games on a Core2Duo. The GTX 750 Ti is fine for the most part, but it won't max out every modern game.
The biggest bottleneck is that Core2Duo, which is, at best, the bare minimum for modern games. You could step up to a Core2Quad, but this offers roughly the same amount of power as a modern dual-core CPU.
If you really want to max the graphics on every modern game, which is a near impossible task anyway due to bad PC optimisation in certain games, you need to change the CPU, motherboard and upgrade the RAM to 8GB. Beyond that, you may also need to change the GPU and the PSU.
As it stands now, your rig is good for medium settings at best.