I'm not surprised by this at all. People, look at this game's sales history:

http://vgchartz.com/games/index.php?name=suikoden&console=&publisher=&genre=&keyword=&order=Last+Updated

The game has quite consistently sold between 200k-300k worldwide, with the most recent iteration selling 190k.

Here is a prediction for you: any game from any genre on any platform that sold 0-300k will not see iterations on the PS3 or 360, no matter how tied to the PS2 or Xbox that original was. I'm sure there may be an occasional exception to that rule, but in general, I expect it to be true. 

The market for a game like Suikoden is saturated. The gaming market is growing, but not this segment of it in particular. This isn't a genre with explosive growth for which increasing revenue can offset increasing development costs. I expect all of these mid-level RPGs like Suikoden, Baiten Kaitos (yes, I know Monolith is now Nintendo, it's just an example) and Marvelous Software games to all be headed to the DS and Wii.

I dont care which sytem it goes to, as long as they make one

 Dang had no idea Suikoden's sales were so low.  Just shows RPGs really don't sell unless they're Final Fantays related. (Or DQ i guess.)

Hah, i'm surprised no one starts any "Square is bad for the RPG Industy" since people like to blame the Wii for other systems poor sales and certain games poor sales. 

Here's a question I've been dying to ask some people: what if some genres never justify the cost needed to make PS3-graphics games?  I'm going to make a bold prediciton: apart from the occasional exception, not only will this be true for thie current generation, but we will absolutely never,  EVER see a game like Suikoden with PS3 level graphics.  There will never be a large enough market to support it.

Some markets are saturated, and will not see much growth. RPGs are an excellent example, actually -- I honestly doubt that the market for RPGs will ever get much bigger than it currently is. The market for games in general is growing, but from what I can tell, virtually none of that growth is being experienced by RPGs.

So here's the question to cook people's noodle with: are there some tried-and-true, we-can't-imagine-the-industry-without-them genres that will simply NEVER grow large enough to justify 20 million dollar budgets with consistency? I think so. Again, there will be the occassional exception -- FF XIII for RPGs is a good example -- but I think we've reached a point where particular genres just aren't going to be getting much bigger, and will never justify a development cost bigger than the ones they have right now.

Again, for emphasis -- I don't mean that just for this generation. I mean EVER. Some portions of this market are as full as they're ever going to get, and some genres are even seeing rapid and painful contraction, such as Fighting Games. 

^^i would guess suikoden V sales were low because its release date was too close to Kingdom Hearts II.

Also part 4 being panned as the worst game in the series likely hurt 5's sales.

Here's a better question: Why do people assume that all games on the PS3 must have perfect HD graphics and be ultra high budget affairs?

yeah, 4 lost suikoden a lot of fans.

offtopic: I wonder what happened to the breathe of fire series..
i remember playing the 3rd one and it was good.

Because otherwise why wouldn't you put in on the Wii.  Though that hasn't stopped some people, for example Disgaea 3.  Though considering how small Nippon Ichi studios is...(or atleast how small i beleive they are) this was probably started before anyone knew the Wii would be a success. 

Either way, there isn't really an advantage to putting a Suikoden game on the Wii other then it being cheaper to make.  I mean it's your basic menu JRPG that takes 2 buttons and a control pad.

It's already been answered by others, but:

1) Because if you arent' gonig to give it great graphics, why not just put it on the Wii?

2) The PS3 is only an example. Do you see how I said "PS3 level" graphics? The point wasn't about the PS3 in particular. If you'd like, swap it out and say "360-level." It's not relevant. The real point is this -- graphics that good cost a lot of money to make, and some genres will absolutely never, ever justify spending that much money on development, because the markets they represent are too small and their growth is stagnant.