My Minecraft looks pixelated

Yep, that's exactly what vanilla (without mods) Minecraft looks like.

There are a bunch of resource packs and other mods to change the look and that's probably what you've seen in those videos you mentioned.

I recommend taking to Google to find the texture packs I've mentioned. Unfortunately mod recommendations are off-topic for our site.

Hate to break it to you but this is what vanilla (unmodified, standard) minecraft looks like. If you wanted any of the fancy crisp HD textures you have to download them separately.

Theyre in what are known as "Resources packs".

Go to a website like say, planetminecraft and download one, follow the instructions and you may run with a custom texture set. If your pc can handle, i recommend a HD pack.

Two ideas here.

1. Minecraft is supposed to be pixelated, it is how it's designed.

2. There may be something wrong with either Java or your GPU. Maybe even something running in the background responsible for rendering, so maybe even your CPU. There's many things that could cause it, but I'm not exactly sure.

This is the best answer I can give.