Why are my games still lagging on my 4gb RAM Lenovo G50-30?

I've tried playing skyrim, just cause 2, dead space 3 and some other games which require 2gb ram to play but they are still laggy as hell and unplayable. I don't understand how it says thats the minimum requirement is 2gb ram to play yet it still lags, especially skyrim. The lenovo has an intel graphics driver and 4gb ram, so surely this would be enough. Even fallout new vegas, which runs fine, lags major in areas with alot of lighting. If i was to upgrade it to 8gb ram, would this solve the lagg? As 8gb is the most i can upgrade it to.

You don't have enough RAM and Gigs hardrive.

RAM is only one fourth of the needs.
CPU is the other fourth
GPU is the remaining half.
Compare what you have to what the games want:
I believe you will see that you fail in two of the categories.

Skyrim…
Recommended Requirements
-Wndows 7/Vista/XP PC (32 or 64 bit)
-Quad-core Intel or AMD CPU processor
-4GB System RAM
-6GB free HDD (Hard disk drive) space
-DirectX 9.0c compatible NVIDIA or AMD ATI video card with 1GB of SKYRIM RAM: Nvidia GeForce GTX 260 or higher; ATI Radeon HD 4890 or higher
-DirectX compatible sound card

Just Cause 2:
Recommended System Requirements
OS: Windows Vista/7
Processor: Intel Core 2 DUO @ 2.6 GHz/AMD Phenom X3 @ 2.4 GHz
Memory: 3 GB
Hard Drive: 10 GB Free
Video Memory: 512 MB (NVIDIA GeForce GTS 250/ATI Radeon HD 5750)
Sound Card: DirectX Compatible
DirectX: 10.1
Keyboard & Mouse
DVD Rom Drive

Games do not give satisfactory play on Minimum Specs,
I too, am stuck with a Just Cause 2 that simply will not run on Minimum specs.