Avengers Annual #7 by Jim Starlin (death of Warlock).  Grade A
Marvel Two-In-One Annual #2 by Jim Starlin (death of Thanos).  Grade: A
Logan’s Run #6 (back-up story only) by Scott Edelman and Mike Zeck.  Grade: C
Marvel Graphic Novel #1: The Death of Captain
by Jim Starlin.
 Here.  Grade: A
Silver Surfer Volume 1 by Jim Starlin and Ron Lim.  Grade: B+
#34, 35, 36, 37, 3844, 45-47 (origin of Mephisto), 49, 50

Thanos Quest by Jim Starlin and Ron Lim.  Grade: B+.  # 12
Spidey Super Stories (non-canon).  Here.
The Infinity Gauntlet by Jim Starlin and George Perez.  Crossed over with  Grade: A. #1, 2, 34, 5, 6
Tie Ins:Silver Surfer #55; Spider-Man #17
Infinity War
by Jim Starlin and Ron Lim.  Grade: C+. #1, 2, 3, 4, 5
Warlock and Infinity Watch #9 by Jim Starlin and Angel Medina (Gamora gets upgraded).  Grade: B-.
Marvel Comics Presents by Gerry Conway and Scott Kolins (Death speaks to Thanos for the first time).  Grade: B-.  #109-111
Marvel Holiday Special (1993).  Here.
Infinity Crusade by Jim Starlin and Ron Lim (1993).  Grade: D. 2-6
Thanos’ appearances from 1993-1996.  Grade: F.  Here.
Ka-Zar by Mark Waid and Andy Kubert (1998).  Grade: F/A (for cornball factor) #7-11
Deadpool #33, 64 (cameos only)
Avengers: Celestial Quest by Steve Englehart and Jorge Santamaria (2001).  Grade: B
Infinity: Abyss by Jim Starlin and Al Milgrom (inker) (2002).  Grade: B-.  Here.
Marvel Universe: The End by Jim Starlin (2003).  Grade: A.  #1, 2, 3, 4, 6
Thanos (2003)
Jim Starlin and Al Milgrom (inks).  Grade: A-. #1, 2, 3, 4, 5, 67, 12

thanos hates squirrel girlDan Slott’s Thanos (Great Lakes Avengers X-Mas Special (2005) & She-Hulk #12-13 (2006).  Grade: B.  Here.
Marvel Adventures Fantastic Four #16 (non-canon, all ages).  Grade: D
Annihilation Event (2006).  Grade: B-.  Here.
Thanos on TV.  Here.
Lockjaw and the Pet Avengers (non-canon, all ages).  Here
#15 (in Pool-O-Vision only).
Avengers and the infinity Gauntlet by Brian Clevinger, Lee Black, and Brian Churilla (all-ages, non-canon) (2010).  Grade: A.  Here.
Thanos in 2010-2014.  Grade: C+.  Here.
Thanos today (includes The Infinity Revelation).  Grade: B.  Here.
Thanos: Relativity (2015). Grade: C+.  Here.
Thanos: The Infinity Revelation (2016).  Grade: C+.  Here.
The Top 15 Thanos Stories of All Time.  Here.