Suikoden II is the best game ever made, in my opinion. Amazing story, excellent characters, entertaining gameplay, plenty of side stuff to do (I love the ever-amusing cooking sidequest) -- it's just all-around a very well made game. Suikoden specializes in mature, intricate plots and II especially did a really good job. Jowy is arguably one of the best developed video game characters, and Luca Blight is definitely a great villain.

I go back-and-forth between Suikoden III and V for 2nd. Really, I think III had better characters, but V had better gameplay. SIII was overall a very good transition to 3D, but in some ways it was obviously a first step -- odd battle system, abbreviated skills system (everything was maxed out by chapter 4), and AoE spells being useless, it could've been better. SV was much more polished. They're pretty close in my mind, though, and SI is not far behind either.

Overall, those four are head-and-shoulders above most RPGs.

IV is the bottom of the barrel. Tactics is probably above it, but I never finished it.