Alright, so today I went on a rather ambitious thing to do with my G5.. I tried to replicate the crunch tone used on Dream Theater's On The Back Of Angels.
Of course, this resulted in quite a massive fail, I used the Alien sim for the sounds and honestly, I don't think it's possible to get Petrucci's Crunchy sound, which is not surprising to me since the total cost of his rig probably make the G5 looks like peanuts xD
Anyway, here is what I can come up with. It doesn't sound anything like the original guitar track, but it might give you an idea of how the G5 sounds like in a band mix.
On a G5, to get Petrucci's crunch tone, I would start with a Mesa Dual Rectifier or Bogner amp sim, instead of the Engl sim. And I would consider adding an overdrive pedal to that at times, such as a Tube Screamer as long as you can keep it on the brighter side.
Alternatively, the MS Crunch (Marshall Crunch) with a boost or overdrive ahead of it. He also uses a bit of chorus at times, etc. and really a lot of things. So getting his tone is not that straightforward and of course a lot of it is his playing style. The reason I say the Engl sim is not the easiest to get his tone is that the Engl sim "Alien" just like a real Engl Invader (channel 3?) is a noisy beast. It's awesome but Petrucci has quite a clean tone. You can use a noise gate, sure, but his tone is cleaner than that most of the time.
Noise gates tend to take something out of a tone and not just cut noise during silent parts. I try to use them sparingly which is not a G3 or G5 specific comment, just in general. Requires a lot of tweaking to get noise gates working to not suck your tone IMO and often not worth the time to me.