The different generations, continuities, and characters tend to have different styles.
For example the anime, and manga, characters often have a black areas above their irises compared to their game counterparts. Also, for example, quite a lot of game characters from the first gen and early second gen really had no actual scleras (or at least black ones).
For comparison reasons..
I'm honestly not the biggest fan of the styles that have black eyes or have a black area above the iris. My favorite style has to be the post-Crystal game style, specifically Gen 4 and 5's.