[Gorgetrapper]

Suikoden 1 - Played in MANY times, will continue to play it MANY more.
Suikoden 2 - Even better than 1, so I guess you understand what happens next.
Suikoden 3 - Almost a full change of the game, except for the 108 character deal, still enjoyable.
Suikoden 4 - This game was "one" of the worst of the series, after I 100% the game, I kept it on the memory card, and will not touch it again.
Suikoden Tactics - Ever play a hard "tactics" game? Well this is it, holy fucking shit is this one of the hardest I've ever played.
Suikoden 5 - Still in the process of playing, not much of a console player anymore, but it seems to be more of an extension of 3 (not the story, the gamestyle), but the story is a lot better.
Suikoden Tierkreis (DS version) - This one is hands down the WORST installment of the series. I still hold on to it, because it's a suikoden game regardless of how terrible it is.

oh I neglected to mention something...

I noticed that with these games, it's all in the same world/universe. So you'll catch glimpses, stories and flashbacks of characters from previous versions of the game. Not many games actually do this, they just recreate a whole game in another world (final fantasy). Don't get me wrong, I love those games too, but it's pretty damn awesome how they can incorporate these games into the same world.