I have to say that sadly, I wasn't surprised when I read that most of the responses said you should get him checked out for behavioral issues. BUT, please remember that in today's age, so many mothers are too proud and too embarassed to admit that it could be anything THEY are doing wrong. It's always, "oh, he must have ADD or autism or be eating something that's not agreeing with his metabolism" Sure, there are exceptions, but for the most part, what these things say to me is "Well, I can't see how it could possibly be MY fault, so it MUST be the child" Let's all start to look in the mirror when our kids are showing out of control behavior and not run to the doctors PLEASE!!!
Your son has you wrapped around his finger. He knows at this point that he can get away with anything and everything and STILL get positive attention from you. When he is screaming because of bedtime, and STILL getting a kiss from momma like he hasn't done anything wrong, my question is why WOULDN'T he continue the screaming? It prolongs his bedtime, doesn't it??
You have a strong willed child who has gained control over you and WANTS to be in control, and the thing you have to do is get the control BACK. So what if your 2 year old is totally fine, that doesn't mean anything except that he is NOT a strong willed child. I have a 7 year old strong willed daughter, and a 6 year old sweet as pie son. You have to parent the two completely differently. With my daughter, I have to have very particular things in place. For instance, if I want her to pick up her room, I say "before you do anything else, go pick up your room" If I just say "pick up your room", I hear every excuse in the book as to why she can't do it right then. When she was your son's age, here are some things I did...When she threw a fit, I walked out of the room without talking or looking at her. If she followed me into the other room, I would pick her up from behind her, take her to her room, tell her she could come out when she's finished crying, shut the door, and hold it shut from the outside. As soon as she stopped crying, I would open the door with a smile on my face and say "OH! You are finished, now you can come play!" and I'd let her out. When I opened the door, if she started crying again, I would say "oh, you're not finished, but when you are, you can come out" It was a power struggle to her the first time, but I hung in there until she got the picture that crying for no reason = time out in room by herself. And, just to put into perspective how well this works, I only had to do it a few times. Now, I never got to the point where all the control was on the kids' side, so it will take you longer, but it's completely possible for it to only take you a few days if you're consistent. I also used the corner a lot. My kids had no ridiculous "naughty chair", they simply stood in the corner, with their forehead touching the wall. They had to stand for usually about 3 minutes, but if they moved away, talked, or were disruptive, I would add on 1 minute each time. If she fought over a toy, I simply walked up to her, took it away, and put it on top of the fridge without looking or talking to her. She had to learn that I was the parent, and the one in control, because Lord knows, she wanted to make it the other way around. If you go to lay him down and offer a kiss and he says "NO!" then say "okay, well, I love you, and goodnight" and walk out. If he says he wants one all of a sudden, explain to him, "I'm sorry, it's bedtime now, so you will have to get your kiss in the morning." If you don't, you'll have a game going where he'll say he doesn't want one, then he does, then he doesn't, then he does. You could even say before you get up to leave his room that it's his last chance for a goodnight kiss so he has the option of getting one before time runs out.
It always gets worse before it gets better. He knows he can break you, so he's going to escalate his behavior to see where that breaking point is. He's going to scream so loud tonight when he thinks you are going to come back in for a kiss that you're going to think the neighbors will call the police, but that's all part of his learning process. You're basically going to have to teach him what his limits are and what your rules and expectations are all over again. Since he has his own idea of these things already, he's going to challenge you because he's used to them being a certain way and doesn't want them to change. But, if you stick with it, he'll be a much happier child. If you can get ahold of just the tantrums by putting him in his room, the bad behaviors that land him in the corner throughout the day, and the nighttime kiss thing, other parts of his behavior will begin to get better too because he'll learn that you are the one in control.