It sure would be nice to place blame for this kind of behavior on ADHD, but to do that, you need to see a dr.
Actually your son sounds like he's bored and not getting the kind of "strokes" he needs. Why is he lying, why is he bullying others? There are no classes in school that teach that kind of behavior. So, where is he learning this stuff.
You need to take a hard look at home and be honest with yourself. Kids generally growup to be what they live. Kids who growup in caring nurturing homes becoming caring nurturing people. Kids who live with bullying and lying grow into bullys and liars. 8 is not to late to help your son change his behavior. Lots of love and structure can help. Good luck!

Those are not the signs of ADHD, so I don't think so. Children do not lie or bully by instinct, he had to learn it from someone. However, it would be foolish to assume that it is because of what he is exposed to at home, unless he spends 24hrs a day at home. The most common place to see bullying is at school, he has likely seen other kids bully at school or may even have been bullied himself. If he plays a sport it is quite possible that he learned to bully there, coaches often demonstrate bullying behavior without even realizing it. Obviously he could have also picked it up from home. At this point it doesn't matter, what matters is how to stop it.
Best thing to do now is have an honest and respectful talk with him about it and have him come up with ways to stop it. It might sound stupid but if he himself comes up with the solution then it is more likely to work. Rewarding good behavior will also help. My favorite idea would be to have him invite a victim of his bullying, to a movie. That works to kill several birds with one stone. He gets encouraged to try and stop bullying because he can see something to work for. When he gets the reward he sees that good behavior can benefit him. Also, they may become friends which will further prevent the bullying behavior.
As for the lying. Explain to him why it is important to you to hear the truth. He needs to know he can trust you with the truth so whenever he tells the truth about something, try your hardest not to punish him or stress that because he told you the truth his punishment will be much less. Hopefully he will stop lying to you at least. The stories that he makes up for his entertainment, unless it is excessive it is an age appropriate behavior so don't worry too much about it.

I think the answer will come out of an honest talk with the child. Find out what his fear is that prompts his lying. Think hard and be honest with yourself, has lying been modeled for him as an acceptable way to navigate life? Does he see the adults in his life lying?

He likes it when people believe his made up stories, is this because his real life is so unbearable he has withdrawn into fantasy? Do you spend time with this kid aside from TV and computer games? Does the family eat dinner together? Talk? Engage in fun activities or bonding experiences?

He's bullying other children - is he being bullied or shamed at home? Does he witness violence? Are people in his extended family in bad relationships?

I think this kid has some deep problems, I doubt it's ADHD

No. I do not think that is ADHD. I am a social worker and had the same issue as a child. I was first put on medication for ADD, then I was put into counseling and then finally at the age of 15 I was so upset with who I was and my life that I tried to kill myself and they finally discovered I had borderline personailt disorder. ADHD is commonly misdiagnosied for bipolar or borderline personailt disorder. The reasoning behind my lying as a child was due to extreme sexual abuse that I kept hidden for ten years. There is a major reason why the child is lying and I am not saying that to scare you but please know, I have grown up to be a sucuessful and kind woman who actually is traveling the country giving talks to the youth about mental illness and suicide prevention. That is what I do for a living and I love changing lives. There is hope for your little one. Try and get a pattern established with the lying. What is he lying about? Is it positive or negitive attention? Who is he lying to and what are their responses? If you can get a pattern you can get a root cause and then work on that. Let me know if you need anymore help... after all, I was in his shoes at one point! =(
PS... HANG IN THERE!