Laptop specifications

I have a lenovo g505s laptop.
It has-
4gb ram
2.1ghz amd a8 quad core turbo boost upto 3.1ghz
1tb hard disk
amd 2gb dedicated graphics card.
I tried playing GTA 4 but it was very laggy. Gta san andreas works perfectly without any lag in full settings. Nfs most wanted(old one) also works smooth but lags in full settings.
My laptop shows 3.2 gb available. Can increasing the ram to 8 gb make it better?
Or is it something else on my laptop which is causing the lag?
Need help.had lots of expectations with my laptop.

It's not fair that I can't make a good comparison because I have an NVIDIA Quadro K1000M and Intel HD 4000 interchangeable graphics processor. (Of course, the game is using the Quadro.) I'll give you what I have just to model it out. It should be pretty equal in Intel equivalence:

My Lenovo ThinkPad W530 Specifications:

Windows 8.1 Professional
Intel i7-3740QM with vPro Technology 2.7GHz up to 3.7GHz Turbo
Intel HD 4000 Graphics & NVIDIA Quadro K1000M (2GB Dedicated)
8GB DDR3 1600MHz

You've got the recommended amount of RAM, but I always go ahead and advise people to go to 8GB when they're playing such an open-world game. I'm truly not a fan of AMD graphics cards because they're cheap and for the casual gamer (like if they're just playing WoW, DotA 2, or something of the like… Not too extreme.) I say give the RAM an upgrade.

You should be able to run those games no problem but your OS maybe taking too much power. Change to 7 or XP or upgrade your ram.