Monster Trucks--like in SA
Quad Bikes (4-Wheelers)--like in SA
Mower--like in SA
Kart--like in SA
Bicycles--like in SA
Tractor--like in SA
Simi-Trucks (able to attach and detach trailers with a push of a button)
Customize any vehicles
Buy houses--like in SA (but alot more with unlimited parking spaces and able to use parking lots to store Vehicles)
Buy vehicles
Customize/decorate houses
Able to rob houses again--like in SA
Jetpacks--like in SA
Parachuts--like in SA
Able to pilot planes again--like in SA
Buy airplane tickets--like in SA
Ride as passenger in any car (friend's car, g/f's car, limo, hitch hikde a ride)
Taxi missions--like in SA
Alot more clothing stores than GTA IV
Alot more buildings to enter/explore than GTA IV
More side missions
Trolly--like in SA (but able to ride them)
If arrested, be put into a police car (like real life)
Racecars--like in SA
Able to customize your characters (weight, muscle, hair, skin color, height, eye color, hair color customizing)