Has a Light Sider EVER won a saber battle where he didn't "dabble in the dark side" (translation: "get angry") to win?
And yes, the Clone Wars are GREATLY exaggerated. Grievous actually is able to dodge the force pushes and throw objects of Jedi MASTERS and slaughter them with ease. He TOYS with them. He's able to leap dozens of feet in the air and CLING TO THE CEILING... apparently the Jedi can't even sense him until he's right on top of them! That and his speed matches or even excedes again, that of Jedi Masters.
His chest being crushed is in there, but in the movies, supposedly mere minutes after that scene, his chest doesn't look damaged in the least. When did he find time to repair it? Why didn't that act kill him, since it should have crushed his organs as well? (And he doesn't even appear to have actual lungs, just a heart, brain, eyeballs and some "guts"). I could be wrong about that though... Perhaps his robot lungs were damaged.
But actually Lucas always intended the character to be coughing. Apparently the CW guys weren't clued in to this, and they just created the scene to explain the sudden change. That's also why they inserted the scene of Dooku training him and advising him to "run away" from battle sometimes (to try to explain why in the movie he claims to have been "trained in your Jedi Arts by Count Dooku" and acts like a coward repeatedly).
The Jedi in the CW are also exaggerated, Mace Windu destroys an entire ARMY of Super Battle Droids all by himself (when in the Geonosis Arena Jedi were dropping like flies against a fraction of the number of droids). There's lots more examples, but that's why I don't consider them accurate representations of the power levels or abilities of any of these characters in the Star Wars universe at large.
Incidentally, the ROTS novelisation has Mace Windu say something like (regarding Grievous) "I have fought him blade to blade, he's more than a match for most Jedi."
Thankfully that wasn't in the movie. Such an event is never depicted in the CW series OR in the movie (in the cartoon, all he does is leap in there and crush his chest, no saber blows are thrown or landed between them).
The CW Grievous is surely "more than a match for most Jedi" but the movie Grievous? I'd be surprised if he could kill more than Padawans or captured unarmed prisoners. Of course the movie Jedi in ROTS go back and forth from being useless to almighty (compare how Yoda and Obi-Wan SLAUGHTER stormtroopers in large numbers, but other Jedi Masters fall to a fraction of them, but also look at that Padawan, Lucas's son, who takes down quite a few troopers before dying). I'm not sure if Lucas was trying to say that Palpatine somehow "turned off" their force powers for a second or two, making them completely caught off guard (but Yoda, sensing the pain of the other Jedi, was able to snap out of it somehow, and Obi-Wan just got danged lucky) so that a few stray shots could get through or what, but still.