I've been away from these boards for God knows how long, and when I come back, I have to go right back into my role as resident Leetch fanboy, so here goes...
Leetch is criminally underrated by most hockey fans. He is viewed as a one-dimensional offensive Dman that was weak in his own zone. And he is viewed as a player that could not get it done without Messier.
Let's make a comparison to our current players. Let's look at the attributes that make us marvel at Adam Fox right now: how he distributes the puck, how he uses his vision to break up plays defensively, his ability to create time and space with the puck where none seemingly exists, his ability to hold the offensive blueline against all odds, then bump those attributes up a level. Then add in the dynamic offensive ability of DeAngelo, bump that up several levels, and you are starting to see the type of player Leetch was.
Leetch was able to take control of a game in a way that I have not seen from another Dman since. Even his contemporaries who are viewed more favorably, like Bourque and Chelios, did not have this ability. When you look at those mid-90s teams, which had players like Messier and Gretzky (past their primes, but still with some greatness left), the gameplan of every opposing coach in the playoffs was centered around stopping Brian Leetch.
So what happened? He did have some struggles post-97. The team as a whole went into the dark ages, and he was playing upwards of 30 minutes a night on terrible teams. For reasons I will never understand, +/- was viewed as a useful stat in this time period. He did still have something left in the tank though. In 2000-01, he led all Dmen in points while playing great D. He should have finished at least 2nd in Norris voting, but finished 5th because no one was paying attention to Leetch and the Rangers anymore. With some better teams and better coaches, he would have had some more high-level seasons later in his career.