The Sentry of course. The Sentry is everything.
What I always liked about the Sentry was the "you", when he first came out. The narration was speaking about him and to him at the same time and in a way it spoke to me as a reader and the fan of comics, power fantasies and stuff like that.
Speaking of power fantasies - the Sentry has it all: His power set covers everything up you would need as such a character. His potential is limitless. He could literally save the entire world, if not ... for his own humanity, which limits him greatly. He has problems. He has agoraphobia and sometimes it's tough for him to do something. I'm sure that many people can rely to that, since everyone should have days where it's simply tough to go on.
I like how Sentry is operating on such a world wide scale and I like that he refuses to take the responsibility, because it's about decisions which you can't make on your own. You can't decide if you will invest time in saving 50 people at one part of the world, while 50 other people die somewhere else, so the Sentry lets CLOC handle it all and simply give him the information he needs. I like the idea of him flying around nonstop all over the world and saving as many people as he can. I like that he is capable of healing people, but rather chooses not to do it, because he would do the same for absolutely everyone and it would cause a lot of chaos... It would bring desperate parents over the edge and they would do stupid things in order to get the Sentry to heal their children, or simply loved ones. If Sentry was not to save them, he would get all the blame.
I also like that he chooses to kill for the bigger picture, like when he ripped Carnage apart. If you're threatening innocents, chances are there that the Sentry is going to kill you and I agree with that. Imagine a child molester doing wrong stuff for the third time and getting imprisoned by Batman once again. Sentry would simply rip that guy apart and all the problems would be solved - parents would be lucky, children would be safe.
In my opinion Sentry is the most believable and relateable comic book character in existence. He truly is human.
I don't want to attack other peoples beliefs at this point, or question their likes and dislikes, but I will still say that I disagree with everyone, who chooses characters like Superman and Batman.
Superman is not inspiring anymore and he rarely ever was. The one time, where I actually really liked Superman was in the short story "Peace on Earth". I also liked "Secret Origins" for the most part, since he was doing there what I would expect Superman to do... helping people.
Superman nowdays doesn't care anymore. I rarely see him actually helping. He is just one of those high herald level brick characters, who brawl it out and go against cosmic threats all the time. He has been disconnected from the humanity by DC many years ago. The most retarded showing in the last years was for me the Earth benchpressing instance, where he wasted 5 days - 5 days where he could have saved countless of lifes, if he was portrayed in a way the Sentry was portrayed most of the time, or as himself during "Peace on Earth" and "Secret Origins".
I hate Batman even more. To me Batman is the most pathetic character in comic books. Not only does he recruit children for his own war against the crime, he continues to does it even after seeing how much bad can happen (Jason Todd's death). He captures his villains (which some of them he actually created) and puts them into Arkham, which has the security standards of my university: none. He should invest his billions to make Arkham a more secured place and not that every McGuyver-level character can escape by simply having a toothbrush. Batman captures the Joker instead of killing him and gives Joker the opportunity to kill hundreds of more people. Batman is just as bad as the Joker and he does it all to not break the law, which he is already doing by being a masked vigilante.
His character is absolutely not-relateable nowdays... I don't see how anyone could ever identify himself with Batman.