From a biological point of view most reptiles are pretty low on the smart scale. If I remember correctly most reptile families evolved roughly about the same time as the dinosaurs did, far predating mammals and birds. Some, like most crocidillians (sp?) evolved even before the dinosaurs and have remained effectively unchanged for tens of millions of years now.
I think a snake will recognize it's owner more through repetitive contact and smell than anything, they could tell you apart from movement and smell/taste from another human but they don't think "Hey, that's my owner, maybe she'll feed me" I believe there are very few animals besides humans that are actually capable of 'thinking', that is to have an identity of self and problem solving skills. But it's a really hard thing to define. I remember from university Anthropology classes that tool use is a defining factor as to whether something can think or not. But there are insects that could be argued to use tools and many intelligent mammals that have complex communication patterns, (whales, dolphins) that do not.
I think emotions are something that is mostly limited to mammals and even then, we try to humanize animal behaviour and interpret them as emotions because that is what we understand when in reality it is just instinct in almost all instances.
Dogs, for example don't 'love' their owners but associate them as dominant pack members and do many things that seem affectionate that are actually submissive so you know they are not a challenge to your authority.
I agree with T.O. saying that they likely didn't become 'smarter' simply because it wasn't necessary for them to do so. Rats are way smarter than any snake will ever be, yet they are prey items. I like to think that snakes are a lot like sharks. Physically they are basically perfect at what they do, so there is no need to evolve further.
I would be surprised if many of the species we have today are really any different from snakes that existed even several hundred thousand years ago. Considering homo sapiens as a species probably hasn't even passed the 100,000 year mark yet that's pretty impressive.
Anyhow, i'm totally just rambling now so i'll shut up