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)