Spectacular sequel.
Lets start with the AI. As soon as I started the story mode I noticed right away the AI is much smarter. The AI enemies now use shields and snipe. The combat is fun and the things they say and shout out are still awesome and funny.
Ranking is great in RS Vegas 2. Whether you're playing in single player or multiplayer your exp will increase depending on how you kill enemies. Also, if you have a rank in RS Vegas it carries over to Vegas 2. So you can unlock things right away if your rank is high enough from the first Vegas. Based on your rank you are unable to unlock a lot of equipments. There are many more weapons to use and make the game more enjoyable.
I find the terrorist hunt mode in Vegas 2 to be much better. Now in the single player terrorist hunt you can play in lone wolf mode (alone) or with your squad. The addition of the squad really makes terrorist hunt better and a litte easier. Though, if you like the challenge of playing by yourself you can choose to play on lone wolf. Some of the popular terrorist hunt levels from the first Vegas too.
Overall RS Vegas 2 is a great sequel and just an exciting game.