I saw a few YouTube videos showcasing a look at most of the machines you can steal/drive/ride. If it's one thing the GTA series doesn't fail at, it's providing a variety of vehicles. I though GTA: San Andreas was pretty diverse with many more kinds of car and motorcycle in series history. This one really seems to offer a lot more including a few different versions of the same machine. For one, the Sultan and Sultan RS. There's even a normal taxi cab, and then a taxi with a different kind of car (the Merit) as well as a taxi van (Cabby). Most of the usual suspect cars have returned with new versions. Those include the Banshee, Infernus, Stallion, Blista Compact, Bobcat, and cars like that.
So here are a some notables I've seen (courtesy of:
http://www.gta4.net/vehicles/ ):
--- Cars ---
* Banshee (has a little Alfa Romeo 8C Competizione look to it)
* Cavalcade and Cavalcade EXT (like a Suburban)
* Cognoscenti (like a Maybach, though I'm not really a Maybach guy... sweet car!)
* Comet (purely Porsche with a Carerra GT-like light design)
* Contender (that's a mean truck... car... Ute thingy)
* Coquette (kind of like a Corvette)
* Dilettante (second-generation Toyota Prius, clearly, with some 1990s Honda influence up front)
* Dukes (clearly a bad ass old-school Dodge Charger)
* Faction (clearly a Buick Grand National)
* Feltzer (I look at it and think Lexus for some reason...)
* FBI Buffalo (clearly a 2003-ish Century Dodge Charger with a cool grill)
* Futo (Toyota AE86 Levin with a sedan look as opposed to a hatchback)
* Habanero (like a Lexus RX-series SUV. I love those and this machine).
* Hakumai (clearly a Nissan Silvia S12 with a little Honda influence)
* Huntley Sport (Land Rover-like)
* Infernus (have the Infernus always been Lamborghinis? Murciélago-like car)
* Intruder (kind of like a Nissan Cedric with some Infiniti influence)
* Merit (like a 2003 Pontiac GTO)
* Minivan (a lot like a late 1990s or early 2000s Dodge Grand Caravan)
* NOOSE Cruiser (Ford Crown Victoria police car)
* NOOSE Patriot (police-customized Hummer H2; most of you know I've gotten tired of Hummers since the H2)
* Patriot (almost always Hummers; H2 here)
* Perennial (very Honda-like)
* Peyote (old-school Pontiac GTO)
* Pinnacle (Lexus-like all around, more like the fourth-generation ES 300)
* PMP 600 (Chrysler 300 in design)
* Police Patrol (uses the Merit; Pontiac GTO-like)
* Premier (Hyundai Accent-like)
* Rancher (I may be wrong, but either like an '80s or '90s S-10 or F-150)
* Ridley (...the bloody hell is this thing?)
* Ruiner (kind of like a Mazda RX-7 FC with a little 1980s or early 1990s Chevy Camaro mixed in (or the other way around))
* Sabre GT (Chevelle with a little Nova mixed in)
* Schafter (very likely a Toyota; Camry with Avalon features)
* Sentinel and Sentinel XS (they were always BMWs... and this M3-like car is no different
* Speedo (most likely a Chevrolet commercial van
* Stallion (lovely car, but unsure what car this resembles... the least I know is that it's a Plymouth or a Dodge)
* Sultan and Sultan RS (most likely a Lexus IS200 with a little Lancer Evo VII(?) mixed in)
* Super GT (most likely an Aston Martin and Jaguar hybrid)
* Turismo (Porsche Cayman S side profile with a Ferrari 360 Modena-like front end)
* Vincent (Mitsubishi-like, but unsure if it's like the Legnum or Diamante or what)
* Voodoo (like the Buick Special in Gran Turismo 4; too bad I don't know the original car)
--- Motorcycles ---
* Faggio (much better than what I remember in "GTA: Vice City." Wished it was designed like the Yamaha T-MAX)
* Hellfury (like a custom chopper, but a bit boring)
* NRG900 (kind of like a Suzuki GSXR 1000)
* PCJ 600 (was a cool sportbike, now a sporty naked bike)
* Zombie (interesting chopper with two car-like tires)
Those are just some notables from me. Still love to play this game in the future. That's even though I said this game may have changed too much to where it isn't as fun to play.