There are some similarities between Darkseid, Apocalypse and Thanos. Mainly with their look. But Darkseid should be done in a way where you feel frightened and fascinated. Thanos just feels like another bad guy alien who is big in size, but he's closed off, he wants to destroy things, he cracks smiles. Thanos almost looks like he's having a good time. Honestly, Spader's voice for Ultron makes that character feel far more intimidating than Brolin's character.
Both Marvel and DC are both guilty of stealing ideas from one another; especially when creating characters. This is why Thanos, Darksied, and Apocalypse seem a lot alike. However there not the same.
You're right Marvel does throw a lot of humor in there movie. However there are dark and serious elements to the Marvel movies. Disney has struck a balance between the two. All though I suspect that will shift with Age of Ultron (which Kevin Feige has said that the Marvel movies would be much dark a starting with Age of Ultron.).
As for Thanos they haven't done anything with Thanos. There not trying to make him scary or intimidating. There trying to get the audience to ask who and what is Thaos story. Remember the vast majority of you're audience don't really follow comic books. They don't want to give the audience everything at once. It's all part of the plan. When they finally do use Thanos then they will make him scary and intimidating for now they want audience asking questions for time being.
I hope Darkseid wipes the floor with him. Fans get two back-to-back movies with Thanos with the second part released at the same time as Justice League's Part 2. Which features Darkseid, probably for the only time. This is not a situation where he will appear in a comedy space opera (Guardians) or in a post-credit scene practically twirling his mustache in a comedic team-up (Avengers). It will be built upon through references, but the big reveal happens in this one Justice League movie in 2019. Darkseid NEEDS to feel like Satan himself as a dictator, with his followers, and whether he comes to Earth or the League goes to him, he has to feel evil/serious as all hell. No fooling around. He's not isolated. Pure business.
First off they haven't even announced a villain for of there movies. Hell for that matter we don't even know who the villain of Batman vs Superman is let alone Justice League. There are so many other villains they could go with besides Darksied. For all you know they are going to go with the Syndicate and do a sort of Forever Evil type story line. You all are just hoping for Darksied.
One things I love his how you guys slam Marvel but Marvel has been extremely successful. There banking in the dough and mean while DC hasn't even gotten started. I keep hearing Darksied needs to be this or he needs to be that. I keep hearing how great all these movies will be and how much better then Marvel will be. Maybe it will be all that but till they do it's all talk. You guys keep going on about how WB should make the films serious and dark but that doesn't prove that will make the films successful. Till they do it and they are successful it's all noise in my opinion.
One thing I'm going to put out there. What if the very things you hate about Marvel is the very thing that has made Marvel so successful? What will that mean for WB if they completely elemental those things from there films? Will the same people who went and saw those Marvel movies want to see DC films that are devoid of the very elements they loved about the Marvel movies in first place?
Bottom line is this WB shouldn't be afraid to use any character they fell would make for a great movie. Disney shouldn't be afraid to use any character they feel will make a great movie. Both company should set out to make a great comic book movie. They should both try and honor the fan and the comics by using the comics a source material while at the same time striving to find ways to make them appealing to non comic book fans.
Both Thanos and Darksied are both great characters. Though I think I prefer to see Darksied if done right.