I try to avoid these discussions because there's SO much to go over and everybody has different strengths.

One thing I've always told people is that you should think of your RP as you creating an entire environment that you present to the reader. Make it your own and make it enjoyable to be in the room (aka in the post) while they're experiencing your roleplay.

Does your writing style welcome the reader visually? Or is it all clumped together in a massive block (or wall) of text?

Does your color coding (if you use any) make it easier or harder for us to follow along? Are you using the color blue too much, which is too dark for some screens? Are you combining clashing colors that mess with the eyes? (like red right next to blue, etc...)

If you add graphics/pics... do they make sense for the RP in question? Do they help tell your story and paint a visual? Or are they just distracting and pointless?

If you add music/media... does it supply a nice background/addition or is it actually distracting? If your RP is supposed to be your character having a picnic with his girlfriend, you probably should not be blasting crazy heavy metal songs in that RP.

Everybody knows the writing itself is what matters the most, but it doesn't hurt to think of it as an entire environment that you're creating for your reader. Figure out what types of things work well for you. Maybe you HATE color coding your text? Then don't do it. Maybe you LOVE color coding and can even do advanced effects on text? Go for it!

There is NO one answer to what a perfect RP is. It's only perfect if you've chosen the right abilities in yourself to display to us and all of them mesh flawlessly.