In rough order . . .
I. The 1975
II. EDEN
III. Marianas Trench
IV. Gotye
V. Blue October
Both Gotye and EDEN are solo artists and while the title of this includes that, most people have just been listing bands so in fairness, I'll also throw out Paramore and Falling in Reverse/Escape the Fate (they're different bands, I'm just uncertain of how I'd rank them, plus their history is kinda interconnected). Also want to note that Blue October is mostly fifth solely because of how little of their overall discography I've heard. Those guys I've had over 9 albums, and I've only heard one to completion (Foiled), plus a bunch of singles and other tracks from the rest of their albums. I do want to listen to it all someday, it'll probably change my impression but I still love what I've heard enough to classify them as an all-time favorite.
Incubus, Chevelle, Breaking Benjamin, Three Days Grace, and 30 Seconds to Mars.
I would definitely consider Three Days Grace one of my favorites during the Gontier era. Haven't really listened to them since he left the band, are they still worth checking out or are you just a fan of the Gontier years too?