The next frictional game.

[Googolplex]

Yes, high-res and photo-realistic textures are very nice!
And they did not slow the performance.

I only create textures in 2048 x 2048 px.
If an engine supports more, then you can create 4096 x 4096 without slow performance. The graphic card memory is big enough in this time and it looks great if textures are looking like a real surface!

It is no problem to create big textures and all would be looking much better. Also why not?

And if you make a perfect compression, then 2048 x 2048 could be little bigger memory usage as standard resolutions. But without compression it's a little bit sharper and runs fast enough.

High-res textures increase graphic quality more than special effects and engine enhancements. Ans it's a simple way.