For the challenge of Ermac vs 3 Goro's, I suggest getting really good at his back+square, triangle, circle combo. It's the combo where he punches, does a windmill punch attack, then spinning roundhouse kick.
This combo is a great follow up to a jump-in punch. It also has enough stun and knock away on block to keep Goro from counterattacking you if you miss. Once I got really good at doing that combo, I used it to kill all three of them and didn't take much damage at all.
When it connects it knocks Goro across the screen so it doesn't hurt to shot a fireball at him while he's getting up.
The only ones that gave me any grief was 298 (deadly alliance battle) and the one where you have to fight noob saibot with all those power ups. Believe it or not 299 was a breeze for me with me spamming the teleport stomp.
world tilting with milleena and kitanna, shooting tarkatans with milenna and baraka from both sides, mileena vs jade and your abilities come slowly back every 10 seconds, subzero vs sindel and you have to do all his specials before winning, baraka with only 1 lifebar vs goro, kintaro and sheeva.
I love how many gamers consider themselves financial analysts.
1: Stryker VS Shao Kahn. I wish the guy who designed this one a really, really bad day. Not funny. Still not done it. 2: Shang Tsung VS Shao Kahn in babydrama. Holy crap I had problems with this one. 3: Quan Chi VS Quan Chi, mirrored controls. Urghhhhhhhh...not done it either, I just can't get a grip on it. It crashes with my mind. 4: Either Jade VS Sindel in on tilted level, or Mileena VS Kitana on tilted level. I hated those so much. Seemed like the A.I played on Turbo-Extreme. 5: Not sure which else..many of them, even the higher ones was pretty easy, even such painful ones as Sheeva VS Goro and Ermac VS 3xGoro.
Nothing compares to the first one though for me.
-War. War has changed. (MGS4) -War. War never changes. (Fallout)
If you're playing a fair fight, I always thought the ones where you have to hit johnny cage's face a certain number of times were difficult. However, if you play like a cheap bastard It's extremely easy.