With underrated, I'd have to say "Above The Law". I mean it is a very good thriller with a solid and interesting plot, well developed characters and fast paced action set pieces. Also Seagal's performance is top notch - and I'm not saying "for an action movie star", but in comparision to "real" actors. Maybe it helped him to base the role in some parts into his own life experiences, but for a first acting role, I think Seagal came through with flying colors.
Overrated...well, that's more difficult...as far as film critics are concerned, none of Seagal's films have exactly been regarded as cinema classics. As a movie I never really liked "Exit Wounds" that much and it was a (pleasant in a sense) surprise to see it make that good box office money all over world.
Seagal's acting was the only good thing for me in that one, he seemed to be having fun with the more comedic character. I really loved the anger management -scene and his Aikido blended quite well with Wire-Fu.
Plotwise "EW" wasn't that special, in fact it seemed quite incoherrent and lacked sturcture of any kind. Bartkoviak is a good director of photography, but as a director he hasn't got any kind of personal vision or talent as a story teller.
"EW" was basically like a 90 minute long rap video with irritating supporting characters (Anthony Anderson & Tom Arnold) and too little dialoque for Seagal.
While not my favorite of his, it ranks right up there for me as one of them. I realize most people didn't like it because it didn't have the bone-crunching that so many base a movie on. I liked it because I think his character was more realistic, more down to earth, more of a real person in this one than many of his earlier ones, showing a warmer, more human side to him, enabling him to flex his acting muscles a bit better.
