Sellout andmainstream are pure hypocrisy concepts. Since the beggining of times, ART was made for some gain purpose like i.e. for a job in the King's palace, to win the love of a Damiselle, or later for profits. Every single modern band starting from the mid 20th Century wanted to be famous and make money... there is no band in existance that want to play for free, just to demonstrate how different they are. STOP THE BULL. Whoever doesn't get to be famous is for one of two reasons: 1- they couldn't get the promotion and sponsors 2- their work sucks, or does not meet the minimum requirements for commercialization, like i.e. a certain amount of followers. One thing is true: the standards of quality and minimum requirements for commercialization are much lower since after the 90's, and still going down, Labels are getting desperate to sell anything, just like the promoters of rap.
@Mohawk: I love Flotsam and Jetsam. Others include: Crimson Glory Kings X Svartsot Theatre of Tragedy
W.A.S.P. Heathen Forbidden Immolation Symphony X
I'm a fan of both Death and Thrash Metal. Cannibal Corpse are overrated, from what I can gather, they received so much attention because lyrics were some of the most brutal. Chuck Schuldiner and Trey Azagthoth are two of my favourite guitarists. If Cannibal Corpse is your only taste of Death Metal, I think you need to go look for some other bands. But anyway, here are some underrated Thrash Metal bands: Toxik - World Circus and Think This are both classics. World Circus cops criticism for the high pitched vocals, I like them though. Morbid Saint - you probably know them already, but for the sake of the question. Spectrum of Death and Destruction System (demo) are both two of my favourite Death tinged Thrash albums. Rigor Mortis - self titles debut is killer. The riffs are so technical and thrashy, high quality stuff that isn't well known. Artillery - best band from Denmark, and yes, that means better than Mercyful Fate. First 3 albums are essential to any Thrash, or metal fan in general. Coroner - great technical Thrash from Switzerland. All albums are great, but I recommend their first 3 especially for a Thrash fan. Helstar - not really well known to my knowledge. But Nosferatu is the best us power metal album I've ever heard. Mortal Sin - great Thrash from my homeland of Australia. Mayhemic Destruction and Face of Despair are must listen albums. Too bad they broke up recently. Holy Terror - Catchy, Thrashy, and just great in general. Terror and Submission, Mind Wars, check them out. Paradox - Check out Heresy, really awesome power/thrash. Stygian - check out Planetary Dustruction. I got lazy at the end XD There are so many more, but check these out for a start.