A - Plot
Similarities: Both these stories talks about what will happen in the future, and Roland gave us a glance, or plotted a scenario, of perhaps what may happen or how it can actually happen. Both stories also shown that warnings were already given earlier. However, it's due to human selfishness that they choose not to take action immediately, thinking that everything is going to be alright, until it ACTUALLY happens.
Speaking of selfishness, there are also characters in the story whom were selfish. In "The Day After Tomorrow", the Vice President of the United States chose not to listen to Professor Jack Hall about the warnings that Jack wanted to give to the VP. It was not until super bad weather came to America did that make him a believer.
Same goes for 2012, although slightly different. Mr. Anheuser, the President's Chief of Staff, knew what was going on, knew the dangers, but decided to go with protocols, which was only to escort important people only. It was not until the persuasion of Professor Adrian Helmsley to the leaders of other countries did he reluctantly let the people on board the "Ark", which he initially didn't.
One last point, and it's kind of typical: From what I've noticed so far, there will bound to be people who survive these catastrophic events. It's just how they survived it. And mind you, some of the things in the movies ONLY.HAPPENS.THERE.
Differences: The contrast here, is due to the title itself, though it just dawned upon my that maybe Roland Emmerich likes the number three. In "The Day After Tomorrow", everything happens in 3 days. Today, tomorrow, and the day after tomorrow, hence the title. Makes sense. Likewise for 2012. The development of the story in the movie took 3 years, before everything happened in 2012, which also, hence the title. Contrast is, one happens in days, the other in years. Hmm....
B - Characters
Similarities: In both these movies, the main characters, which are Dennis Quaid and John Cusack respectively, had their family to take care of. Both these characters had to go to the extreme to make sure of their family's safety.
Differences: Simple. One had to go all the way from South to North to get his son, while the other had to keep his son and daughter out of trouble. Meh.
C - Death of American Presidents
Similarities: In both these movies, both American Presidents died. Unlike Independence Day, where the President was one of the heroes to stay alive, both President Blake (The Day After Tomorrow), and President Wilson (2012) did not make out of the disasters alive. From what I can see, Roland does respect the President a lot, and even though they died, they did not died in vain.
In "The Day After Tomorrow", President Blake made sure that everyone had the opportunity to take shelter in Mexico, as the storm was hitting Washington hard. Upon knowing that there was still a last escort vehicle, he finally decided to escape, but couldn't make it as the storm overwhelmed the vehicle.
In 2012, President Wilson decided to stay behind to let the people know about what is actually going on. He also felt guilty for not having informed them earlier, and decided to stay to be with his fellow Americans, as he was quoted in the movie saying, "I'll be the last President of this country (America)
Differences: How they died. Naturally, both were killed by mother nature. It's just that President Wilson died a more pitiful death. President Blake's death was not shown, although it was made known that the vehicle he was travelling in did not make it to Mexico.
After President Wilson's decision to stay, he allowed people to come into the White House to take shelter. He stumbled along this kid who could not find her father. Deciding to help,