I never really thought about it that way. Love at first sight does exist. For some reason, we can see a person and feel an instant attraction. The attraction is stronger when the feeling is mutual. I think it is about more than appearance. We can feel the energy of the other person, and know that we are compatible.
My answer to this is "yes."
We definitely feel attracted to certain people when we first see them. You can argue (as the first answer does) that this is simply a sexual thing but I do not believe that it is. My memory of myself as a teen is that I was sexually attracted to many women. However, I did not form enough of an interest in every woman to be interested in actually trying to talk to her/get to know her better. Most of the time, I remember looking, being attracted, but not even trying to act on it. With a few people, I was attracted enough at first sight to get to know them better.
But you can't form a deep and lasting love like that. Obviously, deep and lasting only comes with time. Having now been married over 20 years, I can say that my love for my wife has become more ingrained over the years. It is partly a thing of habit -- the result of being there for each other all these years.
So, my argument is that love is both of these -- love at first sight exists, but it changes and deepens with habit.
Very interesting question. I think this is going to be moved to the discussion posting area of this group, because it is a question that is very open and general, with lots of possible responses. So, let me give you my ideas first before everyone else gets there!
I think the response to your question depends a lot on what you think love is. I definitely think that you can lust at first sight, in that you can feel sexually attracted towards someone, but I personally do not believe that you can love at first sight. This is because, for me, love involves being willing to sacrifice your own wants and desires for the happiness of the other person. This is only something that can be developed through time and getting to know the other person. We have all felt strongly attracted to others, but I don't believe we are able to automatically feel willing to sacrifice our own needs and desires for that person straight away. The only possible exception is when you have children. Without getting to know them parents on the whole are willing to show true love in their upbringing and the sacrifices they need to make to rear them.