Saboteur is definitely one of those games where the sum is greater than the parts.
There's stealth, building climbing (lots of it), blowing things up to earn money (something I find less contrived that doing 9283482 almost identical odd jobs like GTA to earn money), collecting cars and guns, meeting lots of interesting characters, and plenty of shooting.
It's not without flaws: The computer AI is pretty bad, which is OK because it makes the game more playable (it would've been nightmarishly hard if the computer were more skilled). The screen tear can get a little weird when driving fast. Some elements, such as escaping a Nazi base alarm, only to immediately return back to the scene of your crimes with the Nazi's none the wiser. But none of these were deal breakers for me.
Some reviewers rip on the realism -- this is definitely "Hollywood WW II Paris" -- it's not realistic, nor do I think it's supposed to be. It's romanticized, and glossy, but the HUGE open world Paris of the game setting is beautiful and very well done. There's a lot to see and do in the city, a ton of life in the city with people going about their business, driving, hocking street wares, etc. It's quite immersive.
The good:
* Very nice visuals -- they may not be "cutting edge", but with all that goes on in the game, everything looks great. The art direction is also top notch.
* Very good voice over work -- with all of the accents, this game could've felt cheesy, but it all worked for me.
* Generally good, varied action -- you'll drive, you'll shoot, you'll blow things up, you'll climb, you'll snipe, you'll do a lot of different things, and you can do them at your own pace.
* Good, compelling story and NPCs to keep you engaged.
* Wonderful musical scoring/soundtrack throughout
The not-so-good:
* Sometimes insanely dumb computer AI that you'll exploit to finish some of the harder levels.
* Can get a little repetitive, but no more so than GTA or AC.
* Non-ending -- were they out of money, or thinking sequel?
Again, it's not over-the-top wonderful at any one aspect of the games it imitates, but the culmination of the parts makes for a very satisfying game.