There's no comparison. Cro Cop's issue is/was a lack of motivation. Chuck's issues are a lack of fundamentals in striking, and declining athleticism, especially speed.
Let's not trot out the "injury excuse." Liddell's been dropped four times in a row now. He's getting old. Plain and simple.
In either case you shold note that lack of fundamentals can be taken care of with sheer back to the basics training. Whereas lack of motivation can be much harder to remedy. CroCop has been figured out the exact same way as Chuck has though as shown by Gonzaga and Overeem who were both ready to take CroCop right out of his comfort zone and show him they werent afraid of his kicks.
he same thing has happened with Chuck he has been figured out and he needs to reanimate himself. Both men need to reinvigerate their fight game. For CroCop this mens he needs a new skillset in his toolbag (A GROUND GAME) Whereas Chucks toolbox is allready VERY deep as shown in older fights.
The problem with Chuck is that its in his head he doesnt need to use them because of all the hype that got to his head. Chucks most successful and entertaining fights (see belfort, Silva and Babalu fights) were comprised of a diverse striking game including back fist back kicks head kicks and takedowns combined with his counterbunching abilities.
Chuck needs to really immerse himself in his old fight videos and whatch the progression of his change and it should be realised he needs to make the transition back to the old Chuck and ofcourse....KEEP HIS HANDS UP.
That being said these days I would pick chuck to SMASH Crop Cop because Chuck does have a ground game and IMO a boxing style that would completely baffle crocop. Ofcourse he could catch chuck with a HK but i doubt it.
He is VERy tentative when he throws them these days and they are hardly full force anymore. CroCop is by no means a tactician whereas Chuck has demonstrated he can be when he wants to be especially againt the big names like Silva, (At the time Tito and Belfort aswell)
Chuck would realise a victory over CroCop would really polevault his slowly waining career back into the limelight and would take CroCop down if he couldnt find his range inside CroCops kicks. Chuck Via decision due to heart something CroCop hasnt tasted in a long while.