I actually enjoyed Suikoden IV a lot, but I agree with you, Suikoden V is way better
While Suikoden IV might be at the bottom when compared to 1-3 and 5, it is still better than most. I did enjoy the "prequel"ness of it and if you have not played any of the other Suikdoen games it would be a good place to start. Hell, while you do not NEED to play any of them to enjoy the others, they are definitely better if you do.
Odin Sphere is probably the most "japanese" of all the games listed above. It is a fanstic Action RPG and it is Atlus in whom you can never go wrong.
Best two Dev/Publishers on the PS2 for RPGs is easily Atlus and NIS for your pure "anime" feel RPGs.