This is gonna be long! Hopefully each actor/series will not get more than one or two lines. My opinion means "not to be disputed"! Well, I try to not be sarcastic and condescending. And insulting. And a general jerk. And...
(Btw SLML refers to the game, "Sakura Wars: So Long, My Love". Just in case more games get domesticated in English.)
Organized by character and/or group:
Teikoku Kageki Dan
Ichirou Oogami:
OVA 1+2: Doesn't sound too old or too young. Pretty much perfect.
TV: Sounds too old. I prefer Corey Gagne as Kazuma Shinguuji.
Movie+'Sumire'+SLML: Prob'ly the de facto Ohgami. Pretty much perfect as well.
OVA 3: A bit younger sounding than my "pretty much perfect" picks.
Sakura Shinguuji
OVA 1: Uh... Idr...
OVA 2: Her voice is mostly calm and even. I don't recall her excited moments well...
TV: Ugh pronouncing Sumire's name as "Sumira" is just WRONG! A bit too stiff and I think she squeaks when Sakura is overly excited.
Movie+'Sumire'+SLML: High-pitched heroine: check! Uh if you like that, then okay. Otherwise, good choice. (De facto Sakura?)
Sumire Kanzaki
Of all the character VAs, I think Sumire is blessed with all NORMAL voices. I don't think I can remember one voice of hers I didn't like. Well, maybe her Movie voice was a bit haughty and squeak-ish, but okay for the most part.
Maria Tacibana
OVA 1+2: Thick Russian accent that I find inappropriate. Though low-pitched.
TV: Stiff. No stupid accent.
Movie+'Sumire': No accent either XD.
Iris Chateaubriand
OVA 1+2: Faux French accent that isn't very French.
TV v.1: No stupid accent. Okay for this version of Iris (aka - "sad Iris").
TV v.2: No stupid accent. I think she played Iris a bit softer in tone.
Movie+'Sumire': Iris is annoying and this voice is annoyingly appropriate.
Kouran Li
OVA 1+2: Wtf is this? Some unknown, lisp'y accent. Stiff.
TV: Idr *shifty eyes*. No stupid accent though.
Movie+'Sumire': Okay. No accent, so it's fine.
Kanna Kirishima
OVA 1: Confidently played and not weepy. Not that Kanna gets emotional much in 'Ouka Kenran'.
OVA 2: Squeaked when Kanna apologizes, but I think that added to Kanna's inner-child.
TV: Omg shoot me. The worse "man" voice ever.
Movie+'Sumire': Okay iIrc.
Orihime Soletta
No one really played Orihime terribly. Though her Movie voice plays whiny at the right time.
Leni Milchtrasse
Same as Orihime. Though her Movie+'Sumire' voice is EXACTLY THE SAME as Izzy's from Digimon (well, they share the same VA).
(Let me know if you want to read about Yoneda, the Fujieda sisters, Kazegumi, and others from Tokyo!)
Paris Kageki Dan will go under here...
New York Kageki Dan will go under here... ...