Hey, this is really fun. Just so you know, I don't speak a word of Greek. And I've figured out dissapointingly few of these. I think we need to make a team effort out of this...
I'll start with the obvious ones:
Leyeon ton (H)yper-(h)eroon=Legion of Super Heroes
Koritsi tou Kronou= well, koritsi means girl, apparently, and kronou sounds like it has something to do with time. Kid Quantum? Oh, no, wasn't Chronos the god of Saturn? Saturn Girl!
Kosmiko Pedi=obviously Cosmic Boy
Nearos tou Keravnou/Astrapis=no idea, but because of the order I'll say Lightning Lad
Pedi tou (H)eliou=Sun Boy!
Breniak Pente (name untranslated. If his name was to be actually translated it'd be Enkefalikos Pente)=Brainy. I think we should start calling him Enkefalikos
Pedi-Hameleon=Chameleon Boy
(H)yperkoritsi= took me a minute, but Supergirl!
(H)yperpedi= Superboy
Pedi-Topi= Topi Boy? No idea.
Aorato Pedi= Ditto
Mon-El (obviously)
Kopela tis Skias= Sounds vaguely like it should have something to do with sky. Dawnstar?
Koritsi ton Oneiron= Shadow Lass? Oneiron sounds vaguely like something dark...
Chemikos Vasilias=Chemical King, obviously
Pedi tou Karate=Karate Kid
Koritsi tis Nyktas=Night Girl
Nearos ton Stoiheion (Alchemistis)=Element Lad
Agori ton Astron=Star Boy?
Dropali Violeta=Shrinking Violet
Kolossiaeo Agori=Colossal Boy
Lefki Mayissa=??? the White Witch?
Prinkipissa Protzektra=obviously Projectra
Oultra Agori=Ultra Boy
Kopela tis Molynsis=kopela apparently also means girl. But molynsis is a mystery... I'm going to say Dream Girl, just 'cause
Tyrok=obvious
Agrio Pyr= no idea. Wait, Wildfire! (Pyro from the X-men helped here)
Tripli/Tridimi Kopela (Dipli Kopela or Kopela-Duo)+Triplicate Girl
Kinitiki=Kinetix
Koritsi Fantasma=Phantom Girl
Siderenio Agori= no idea
Astro tis Avyis= wait, I already had something with Astron (I'm so confused!)
Monos/Monahikos Lykos= Timber Wolf! (I love this one. Lycos would be a cool alternative name for him)
Kopela tis Astrapis/Keravnou=Now I'm pretty sure that the one above is Lightning Lad. This one is Lightning Lass.
Agori Ylovoros= voros sounds like it has to do with eating. Matter-Eater Lad?
Poliko Agori=Polar Boy?
Agori tis Petras= Stone Boy!
Pedi tis Hlorofylis=Chlorophyll Kid!
Nearos tis Fotias=don't know, but the obvious sub missing is Fire Lad
Vasilissa ton Entomon=Insect Queen! (I know this because of entomology class...)
and some villains:
Payideftis tou (C)hronou=Time Trapper (wait, this chronou is spelled differently than the kronou from above...)
Mordru o Magos=obvious
Koritsi Arahni=no idea. Wait, Spider Girl?
Pedi tis Nemesis=Nemesis Kid
Smaragdenia Aftokrateira=Emerald Empress
Ypohreotis=Persuader? (Just because of the placement in the list...)
To Heri (or simply Mano/The Hand in Italian)
Tharok
Validus
Komputo o Kataktitis
Doktor Rigulos
Let's see, that leaves (I've only removed the ones I'm pretty sure about):
-Pedi-Topi
-Aorato Pedi
-Kopela tis Skias
-Koritsi ton Oneiron
-Agori ton Astron
-Lefki Mayissa
-Kopela tis Molynsis
-Nearos tis Fotias
-Siderenio Agori
-Astro tis Avyis
-Nearos tis Fotias