I would rank 3 last, even after 4. It must be because it was the follow up to 2, but I just really disliked how drastically different it was. The battle system, the switching between characters, I thought it was all a step in the wrong direction. 4 made up for it by going back to a more normal battle system even though there were only 4 party members, and focused on one character. 5 was definitely more of that classic Suikoden feel, my only complaint being how long it took to get your True Rune, at least to me it felt like I was pretty far into the game/story before I got it. If there ever is a 6 I pray it takes place after 2 or 3 and there is plenty of callbacks to previous games.