First, it should be noted that comic books and movies are a very different medium and certain things that work well in comic-form would be rather silly on screen. There are some aspects of Thanos in Avengers: Infinity War that aren’t in the comics but work really well. And there are also some aspects of the character in the comics that are great, but wouldn’t work on film. Neither interpretation is necessarily superior, they’re just different. Comics have also been around for many decades so a lot of authors have had a hand in writing and creating the various characters. This means that very few characters in the comics have been consistently written for their entire existence. Whereas in the MCU, there’s a very clear continuity beginning with Iron Man in 2008.
As many have acknowledged, Thanos in the comics is largely motivated by his love for the physical embodiment of Death. In order to win her favor, Thanos pursues the Infinity Gems so that he can prove his love by giving her half the universe. But he’s ultimately unsuccessful and throughout his entire comics history, his love for Mistress Death has never been reciprocated. In fact, at one point she makes him immortal so that he can never feel her embrace. In Avengers: Infinity War, Thanos is seemingly motivated by an altruistic goal: saving the universe from overpopulation. The deaths he’s caused have been in the pursuit of saving the universe’s finite resources. This is a more realistic and understandable motivation. Even though his love for Mistress Death is more well known, Thanos in the comics is also concerned with overpopulation. Before the famous Infinity Gauntlet saga, Thanos has a conversation with the Silver Surfer where he explains the dangers of overpopulation: