I played games long before I learned English, (in fact, I learned a lot of English because of games) so when I was a kid I mispronounced everything.

Sometimes, I minterpreted stuff . For example, you could recruit magi if you played as a Wizard in Heroes of Might and Magic II. "magi" means magic in Swedish, so I thought for a long time, that English wizards simply called themselves "magic".

As a French-Canadian, I grew up pronouncing the Bros from Super Mario Bros as "Bross" instead of "Bro-z" and to this day that's still how I say it in conversations.

For VGC specific names, I pronounce ioi: eye-oh-ee for some reason and I used to read badgenome as Badge-nome but I corrected myself now and read it bad-genome.

for some damn reason i used to read halo's master chief as master chef

also i used to pronounce pachter as patcher

i cant get why a lot of people cant pronounce Hwoarang....

I used to pronounce Nintendo as Shauwitznindo, but it is actually ni-n-ten-doh

in the philippines he is also known as Koopa :)

Seriously, who didn't?

I can't think of any major ones but off the top of my head both from FF7 - Tifa as 'Ti-fa' yet apparently it's 'Tee-fa' and Sephiroth I just randomly missed the 'i' out and said Sephroth.

When I was a kid, I use to pronounce Gran Turismo wrong.

Street Fighter II + CPS1 sound chip quality + lack of english knowledge of the average spanish guy in the 90's + non-original Street Fighter II cabinets were a deadly combination back in the day.

You could hear people saying things like "Viper" instead of "Tiger" for Sagat's moves or "Aryuken".

I used to pronounce a lot of names wrong. Until I started learning Japanese.
Yoshimitsu, I pronounced incorrectly. The I makes the same sound as the two "E's" in "eel," so, it's pronounced "Yoshi-MEET-su.
Jin, for the same reason as above, JEEN.
Ryu... lol, you can't even pronounce his name correctly without having some knowledge of the Japanese language. It's not Rai-yu, Ree-yu, or Roo, and there's no way I could explain how to say it properly with roman characters. It's something you have to hear, because the Japanese R and english R aren't the same.

Another one... Blanka... Some people say "Blahn-ka" and others say "Blank-a" I don't know which is correct, but, I'd assume the 1st.

Back over to Tekken, I pronounce Hwoarang correctly, only because I've heard it for so long. I think it's hilarious that the announcer for SFxT got it wrong... Calling him, "How wrong" The W comes before the O...

Another that I'm not 100% sure about is Lili, to be honest. She's my number 1 main ever since Dark Resurrection, but, I'm not sure how it's pronounced. Her full name is "Emily," so, by that logic, it should be pronounced "Lee-lee," but, listening to all the announcers, they seem to all say, "Lilly."

Onto virtua fighter,
Kage Maru, probably my favorite character in the series (not my best, though, funny enough) I used to call him "Cage," but, it's "Kah-geh."
Akira is another I used to get wrong, calling him, "a-kear-ra," but, it's "ah-ki-ra," but, because of that japanese R, sometimes people think I'm calling him "ah-ki-la," which just confuses them, lol.

Funny thing about all this... Mortal Kombat.
Raiden, is supposed to be pronounced the way it is in Metal Gear (but, in metal gear they use the english R, so technically, it's still wrong." Like the pokemon, "Raichu"

But, Ed Boon got the name "Raiden" wrong, which lead to him being called "Ray-den." So, because of that, I spell his name "Rayden" and people want to say I'm wrong for that, lol. Eventhough, in some versions of mortal kombat it IS spelled "Rayden" and not "Raiden."

Then, finally, Shuma Gorath and Dhalsim were two others I used to pronounce wrong. (Thanks, Marvel Vs. Street Fighter) I called him, "Shuh-ma" and not Shoo-ma, and I used to call Dhalsim, "Dale-sim," like in simulator. But, it's pronounced "Dahl-SEEM.

There are others, from Street Fighter like Sakura, and others I used to get wrong, but, I could go on and on and on.

EDIT:

Because I'm nice, I'll link to how Ryu's name is supposed to be pronounced.  However, most of you here are going to hear it as "Du" because the Japanese R is kinda like an L, R, and a D fused together.  Which is why there's no way I could type out how to say it.

It's the very last button, on the page.  Scroll all the way down, and you'll see, "Rya, Ryu, Ryo"

It may or may not help if you listen to "Ra Ri Ru Re Ro" first. and "Da de do"  There is no di or, du, so ji and zu is there, but, ignore those.

http://animeworld.com/japanese/lesson1-1.html