Personaly I think that in all the scenes of LWW Aslan was just perfect! I don't know how they did it, but every time Aslan appeared on screen you feel this sense of...I don't know how to describe it. I remember the first time I saw LWW, when Aslan steps out of the tent, you first see his paw, and I just held me breathe, because I knew that they couldn't have used a real lion, but he seemed so real. It was like they just took him from the book and put him into the movie.
Prince Caspian...weeell I can't think of any scenes that I was very unhappy with, but it didn't seem quite right. I loved the scene where Aslan jumps on the soldier, and overall everything was good. But it definatly was a step down from LWW
And VDT!!! I can't even begin to say how unhappy I am with Aslan. Thr animation was just horrible. He seemed like a character from a computer game. I understand that they had less money, but still. He didn't even look real, and there was hardly any emotion on his face. A very big disappointment.
I just LOOOOOVE Liam Neeson was the perfect choice for the voice of Aslan! I mean he was just AWESOME! I mean every time I see him in different movies, I'm like "" Hey Aslan!". You could close your eyes and just imagine Aslan saying that. He has such a deep, understanding voice. A voice that seems to know everything. And since I wached the movie before I read the books, when I started reading the books I could just hear Liam Neeson in my head. Very, very good choice!

@De_De: I agree completely! Could not have said it better.

I really loved Aslan in LWW, I felt they really nailed his character.
But in PC and VDT, something was just lost.
He just didn't have the presence that you were instantly drawn to, like he did in LWW.
If they ever reboot Narnia, I really, really hope that Liam Neeson would be willing to voice Aslan again! I seriously could not picture anyone else's voice. His voice was exactly the type of voice I pictured when I first read LWW.

The reason he didn't have that presence in the later movies was because he didn't look so real. He portrayed less emotion. I know that in LWW when Susan and Lucy are walking with him to the Stone Table, you can just see it in his eyes that he is sad. You can just see it even from the way he is walking.
Oh Liam Neeson had better. I can't think of anyone who could talk for Aslan!
What I love so much about Aslan is that he so unpredictable. He always appears when you're not expecting him, and doesn't when you're sure he should. I really love his sayings like "I call all time soon" and "I tell no one any story but his own". You know he has the answer and you just want him to come and make everything right. But he has his plan and his own timetable. Just like God does. I think C.S. Lewis did a great job of capturing the essence of Jesus and putting it into Aslan. Aslan's character is so complex, but at the same time so simple and at the same time almost child-like.

1. Aslan was very amazing in all of Walden LWW to be honest. He was powerful, a true king, and the hero. I loved His appearance in Lucy's dream in PC. Even in VDT, I liked the scene after Lucy tried the spell. He was angry, but He forgave her with a loving grace.

2. Where did Aslan go wrong in the Walden? I wished that in VDT he was more prominently featured as the hero. It was pretty disrespectful to the book, considering he saved the crew many times.

3. Yes! Liam Neeson's voice is very powerful and royal, just like Aslan is meant to be.

What? We can't mention Aslan from the Radio Theatre adaptation or the hard to find Brian Sibley BBC full cast adaptation? (I've only heard LWW from the last but I remember it as having a very good Aslan.)

On the whole, I found Liam Neeson and his counterpart in the BBC version acceptable, gentle Aslans. In LWW and VotDT Neeson delivered stern rebukes but it still lacked the depth and range I keep wanting Aslan's voice to have.

What? We can't mention Aslan from the Radio Theatre adaptation or the hard to find Brian Sibley BBC full cast adaptation?

Yes you can. I just didn't think to list them.

BBC:

1. The following of Aslan up through the reaching of Aslan's How at Prince Caspian. It was book perfect and showed the kids one by one getting to see Aslan.
2. I know it was a puppet, but I disliked the extreme lack of mobility of the character overall.
3. It needed more depth. I never really pictured Aslan with a particular pitch of voice, but the fact the tone was very flat was a bit disappointing.

Walden:

1. The scene where Peter, Susan, and Lucy get to meet Aslan for the first time was just absolutely spot on.
2. I dislike the overall lack of power over Narnia that the writers seemed to subtract slightly from the character. Probably most noticeably to me in the scene where he tells Peter that "I too want my family safe."
3. Better than the BBC version as Liam Neeson has a much more dynamic tone to his voice. I wish it had been a hint deeper, but overall I really liked it.

I feel the original voice actor was rather more humorous, although Liam Neeson was never a bad choice.

When I first watched PC, I noticed how short Aslan was during the celebration scene at the end:

Possibly a clever nod to his infamous ability to change size.