Well. I'm a dork, apparently - but I think Yusuke's by far the most attractive. Handsome in a rugid boyish way, yet soft and beautiful too. =D I see it. I'd hit that. Just sayin'.
Yusuke almost strikes me as a Jensen Ackles kind of hot. Rugid and hot, but so ********' pretty you aren't sure what to do with all his damn cute. XD

And though the Beautiful Suzuka isn't as beautiful as he thinks - I think I'd have to place him in second for best looking male. I <3 me some Suzuki. But, Koenma is a good tie with him - I'd place him up with Yusuke, but there's something too ...pretty about him. xD And I'm not one for boys being too pretty.
Kurama is cute to me. Simple as that. Like ...huggable and all that, but not "beautiful" or "sexy". He's a cute-like pretty, and I want to put flowers in his hair and stick him on my shelf and giggle at his adorkableness kinda thing.
Like a pikachu.
Hiei is simply cute to me as well - though not like Kurama. He's not pretty, that's for damn sure. And I don't want flowers in his hair. xDD I like when he pouts, the most - but when he looks all badass - I still think "Cute. <3". He's little, almost like a bitchy cat that you're certain you can make purr if you ruffle the fur on their head enough. XD
Kuwabara's cheekbones look like they'd be absolutely astounding. XD Like. James Marsden. <3 But redheads aren't my thing at all, and he's got the pale, orange-haired, macho look. I think he'd be more my "type" than Hiei or Kurama though. xD
I also highly believe in personality giving a sense of attractiveness to someone. And Yusuke will make silly face, and he's extremely expressive - and he may look silly, but in the end, all of him is what makes him so hot to me. xD (I have to admit Hiei's badass, cold ways make him a little more hot to me than I'd normally think, or being willing to admit.)
I think that's partially what makes Kuwabara a little more attractive to me, despite his horrible orange curly hair. I'd marry that boy and bear his ridiculously gross ginger kids. <3
(I'm sorry if that offends ANYONE. Not everyone with red hair is gross - and it's generally men I find it unattractive on.)