I think it depends on what one really wants to do with their licence. If you're hoping to make a career out of flying then a C152 might be the most cost effective as they're normally a cheaper rate than a C172.
I've flown C152's, C172's and PA-38 Tomahawks. My favourite has to be the C172 for it's stability, but both the C152 and 172 are quite reasonable to fly. The Tomahawk is a different game all together. A nice plane, but not as forgiving as the Cessna's.