The first thing I though when I read the thread title was go outside and get some exercise.

I haven't had experience with most of these, but I will give thoughts on the ones I have.

Star Ocean: The Second Story - I don't recommend it. I'm several hours in and it hasn't done anything to make itself stand out as a game.

Tactic Ogre - I didn't think it was nearly as good as people give it credit for, but if you do like it as others do it would be extremely engrossing. I would recommend you try it highly. (I am super picky with SRPGs)

Suikoden Tactics - Only played an hour or two and found it quite uninspiring. But I have to say the same about Suikoden in general (minus the only giving it a few hours) so you may like it.

Valkyrie Chronicles - I don't know where you got Gundam from. (On a side note it would be sweet if they made a Gundam game that didn't suck). I absolutely LOVED the game in the beginning, but as it progressed the game was more about scouting than combat, which I found exceedingly boring. I enjoy taking the units I have and figuring out a way to dispatch the enemy as quickly as possible, whereas it was progressing into a game where you have to slowly and move your formation across the map keeping careful to spot any eliminate any enemies you encountered along the way. Way more realistic, and a lot less fun.

I'm going to tell you to spend time playing new games instead of replaying your old ones, but if you are anything like me you won't listen to the advice anyways.