Wolfenstein is amazing. I just recently played through it twice. Once on the hardest difficulty starting out. Then I replayed through it again on normal finding everything.
My first playthrough I upgraded your "standard" WW2 weaponry. Second playthrough I upgraded the other guns. I will say this right now. If someone doesn't like Wolfenstein, **** them!
The shooting is fluid and fast. Headshots are beautiful. The guns sound INCREDIBLE! The graphics are damn nice. Lots of collectibles in the game. The powers are all fun in their own way.
Not to mention you can upgrade each gun you find (8 or 9) and each of the 4 powers. There is no way you can fully upgrade everything in the game so 2 playthroughs minimum to really "see" the game.
All in all, it capitalizes on what makes an FPS good for me. Great sounding guns (you really sound like your ruining someone's day), aiming that is fluid like CoD, upgradeable weapons during single player, weapon wheel ala Resistance 1 (find weapon never lose it, just buy ammo when depleted), guns FEEL right. Even the Panzerschrek which I typically hate Rocket Launchers in games, is awesome.
Also, its somewhat free roaming in that your have a few big hubs of the city and you exit different areas into what you could call BIG maps. The cool thing is that the enemies respawn in the city and as you progress, they upgrade. You will start seeing some of the more special enemies as the story gets further.
I would rate Wolfenstein as a 9.5/10 in terms of single player only.
Only cons I can really think of is, the difficulty ramps up quickly. Even on Uber, you might breeze through the first 6-7 hours no problem, but then it becomes REAL damn hard.....instantly.