For me simple and selective or unigue games is good because having lot of games will make the site looks not familiar eve after many uses.
Having instant deposit and withdrawal for crypto currencies will make them as good one.
The games that are offered is the first thing people will check out and unique games let the casino stand out. I liked it when i saw minesweeper popping up.
On the deposit part, i would love to see lightning support getting traction so we can benefit from instant deposits.