I am 25 years old and remember many of Tyson's fights, from watching them live with my father. He (my father) is the reason I am a fan of fighting today.
I am not by any means a fan of Chuck Liddell. I am neither a fan of Tyson.
If it were Tyson in his prime and Chuck in his and it was a stand up fight, then Tyson would probably win. Chuck would surely not be stupid enough to stand up with him though. Chuck is a mixed martial artist and could lkely take Tyson down and work on him there. The only problem with it is getting inside. Tyson would not have a chance in hell against Chuck today. Tyson couldn't beat an average boxer much less a highly skilled MMA fighter.
I don't believe people think Tyson would crush him. He has a puncher's chance but not as good of one because Liddell is so counter active and could clinch as soon as he missed. Likely Tyson would over pursue and end up getting kicked and kneed until he was taken down. Liddell would win the fight under MMA rules.