The best coming of age television series ever. It tugs at your hearstrings, makes you laugh, and gives you true insight into life in the process. You could truly relate to Kevin's ponderings and home life, no matter what your family was like. It dealt realistically with the way relationships evolve and how real life lessons are learned--through experience. Kevin's ponderings were more insightful, and self-aware then most, but the series never become too over the top or dramatic, as it was rooted in the impact that normal day to day life and experiences have on the emotional lives of most people.
Although it was called overly sentimental by some critics, I think that it wasn't and had the right touch of optimism, hope, disappointments, funny moments, and worthwhile insights. Things didn't always turn out great for Kevin, and at times he misunderstood or interpreted a situation, but the nugget of truth about life or humanity was found by the end of the episode. These were good people, living in real life constraints and concerns, and finding the sometimes humorous and sometimes heartfelt meaning from it.
The series did flounder in its later years, as it dealt with an almost grown Kevin, and seemed unprepared in how to maintain its tone while Kevin became more world-wise and less innocent. Basically, the series was about coming of age, and Kevin basically was nearing the end of that phase. The quality of the writing was also difficult to maintain later in the series, as it seems that the inspiring coming of age moments had already been dealt with, and the series wanted to avoid dramatic soap-opera like twists and turns, like other series, and keep the show grounded.
It was an admirable attempt, and I think the next great coming of age series will have to plan its seasons out better, and be willing to take creative risks to tell less plot-driven stories and yet keep the audience engaged.