i've only ever played suikoden 1, which was of course amazing. as for the others, i used to watch my brother play them when i was little. from what i remember...
1 - only one i played, i was dead set on bringing gremio back to life, and fucked up on my first file because i didn't recruit that one dude from that abandoned town before mathiu dies, since mathiu is actually important for that quest. i was so fucking pissed because he was THE LAST STAR and he just so happened to be the ONE GUY who you wouldn't be able to recruit during the endgame because mathiu dying is unavoidable and part of the plot
2 - my brother tried in vain to save jowy, but he didn't realize he never could because he didn't save nanami, and when i saw that you needed to have all 108 stars before nanami gets shot, i was like "wow, well that sucks"
3 - watched brother play this, vaguely remember plot, thought hugo was kawaii
4 - the default/canonical name for the main character is lazlo. that is all.
5 - yo there were some tracks on the ost that slapped. actually this applies to every suikoden. otherwise i only vaguely remember the plot of this one
as for eiyuden chronicle, my brother asked if i heard of it, and i hadn't, but i guess i'll check it out maybe, since it's like a spiritual successor to suikoden or something?