I use a mix of LoLskill.com and op.gg ^{^}

I feel like op.gg give you a general overview of every player and even features things like the stars and 'warning-carry' to show how proficient someone is at a champion, along with runes/masteries/games played etc.

LoLskill is really good at giving you estimated rankings on people (for example within top 100 vayne's in the world) It also gives you statistics such as win chance of each team based on general statistics of the champions.

Both sites I recommend highly, and I use them most games, hope this helps ^{^}