piscian said:
I think this one of the mistakes in F&I. Martell seems to be all chill good guys if a little spicy and the realm is all sandy beaches and kickass food. Pretty much vacation/party central.
I think it's less a question of them being "good guys" as them being the most progressive or liberal of the seven Kingdoms, and thus a bit closer to modern values than the rest of them. Simply by virtue of promoting absolute primogeniture over cognatic primogeniture, they enjoy the support of the vast majority of female viewers/readers. It's hard to get excited about "swearing fealty" to a faction if the best you can hope for is that you get married off and pumped full of children.
Having read the recently released World of Ice and Fire, I'd PROBABLY lean towards Tyrell, upjumped stewards or no. The Reach is probably the least war-torn of the seven kingdoms, and has had the least tumultuous history. Second place would likely be the Lannisters, or the Arryns.
Dorne has enjoyed a particularly bloody last 200-300 years, most prominently in their resistance to Targaryen rule, and some of the methods employed in that resistance definitely calls into question their status as "good guys". The North is very grim, hard and martial, and has spent a great swath of its history fighting wars (many of which they were the instigators of). The Stormlands took 95% of the brunt of the seemingly endless Dornish insurgency, and if not for Storm's End would probably have changed hands even more times then they already have. The Riverlands get invaded semi-annually and spent a distressing amount of time under Ironborn rule. And speaking of the Ironborn, they're probably the only people in Westeros even less cheerful than the Northmen. They're in a perpetual state of conflict, either reaving or getting crushed under some larger nation's boot.
Curious why OP did not include Targaryen in the poll. That'd be an interesting selection as well. Some of the realm's most openhanded and progressive rulers were Targaryens. There's a reason for all the speculation that a landed Daenerys might actually gain some measure of popular support were she to attempt a coup.