1366x768 vs 1920x1080 gaming

Solution
1080p is far better for the more modern games such as Battlefield 3 and Crysis 2+3 etc. The main reason being there is more detail in the game world, and so a higher resolution means more pixels, meaning more detail on your screen. A lower resolution gives you less pixels, and so less detail.

Think of it as a piece of gridded paper, and you're trying to fill in squares to make a circle. The smaller the grid, (resolution) the less squares (Pixels) there are and so the circle will appear more square and less rounded. But with more squares the circle will appear more rounded and less blocky.
1080p is far better for the more modern games such as Battlefield 3 and Crysis 2+3 etc. The main reason being there is more detail in the game world, and so a higher resolution means more pixels, meaning more detail on your screen. A lower resolution gives you less pixels, and so less detail.

Think of it as a piece of gridded paper, and you're trying to fill in squares to make a circle. The smaller the grid, (resolution) the less squares (Pixels) there are and so the circle will appear more square and less rounded. But with more squares the circle will appear more rounded and less blocky.
 
Solution
Yep. It's just the number of pixels on screen. It's especially noticeable in areas of fine detail or things like telephone wires where lack of pixels can make patches of the wire invisible (you know what I mean 🙂) or distant enemies in the sky appearing as just a few scattered pixels etc...
 
PPI is more important than the amount of pixels themselves. Ie, a 27 inch running 1920x1080 has less PPI (Pixels per inch), then a 21 inch running 1920x1080. So a smaller screen could have a smaller resolution and still look the same. a 27 inch panel running 1440p, has the same PPI as a 21.5 inch monitor running 1920x1080. So screen size is really important.
 


Not quite true. PPI does make a difference somewhat to the quality of the image yes, but it is more to do with the overall amount of pixels. More pixels = more image. less pixels but higher PPS = same amount of image, just smaller. PPI is something you get into when deciding upon a monitor size. I myself have opted for a 27" 1080p monitor, as this is the optimal resolution and PPI for my viewing distance. Trying to use a 55" 1080p monitor in the same place would make the picture look terrible, due to the lower PPI.