A little bit about Aizen, in twenty truths format. Of course, given it is Aizen, how much of it is truth, even to himself?
1. Aizen's fearless visage is not a facade. Ever since he could remember fear was, at best, a distant emotion. It is not because of his megalomania, it isn't because of his arrogance or even because of his truly exceptional power. For Aizen there is nothing to be feared - there are mysteries to be understood. That is why Ichimaru Gin is one of the few people he actually fears. His Espada would be amazed to know that he is wary of Orihime for the very same reason as well.
2. For a superb manipulator, he is barely decent at chess. Yet for Aizen there is no contradiction. Chess pieces are compliant, obedient and lifeless - going to their death with no word of complaint or original thought disturbing the pattern. After centuries spent building such patterns he knows it is never so. Ironically, Kyouka Suigetsu is excellent at chess which amuses them both.
3. His allies and enemies alike think that hiding the true abilities of his zanpakuto was an example of Aizen's foresight and ability, considering how much skill it took to do it over the centuries of Aizen's service in shinigami ranks, in combat and out of it. The truth is it took Aizen over a century to realize that the confusing mist of Kyouka Suigetsu wasn't a shikai at all. He still isn't so certain about his bankai, but he doesn't mind. It is too amusing to, and gives him and his sword something to discuss over a cup of tea.
4. He enjoys music, like every proper megalomaniac should. However, in his usual fashion, he breaks the mold and instead of monumental classical pieces like Wagner, Bach or such he prefers the fresh and energetic sound of good old rock, both the harder and the softer qualities. He was probably the only captain to do his paperwork to the sounds of the Beatles, Deep Purple and Queen in Gotei 13 history. Kyouka Suigetsu, on the other hand, loves smoky jazz and blues.
Ichigo would be rather dismayed to learn that he and Aizen share the taste in music, as do their respective swords.
5. Aizen misses his glasses. He never needed them - they were his disguise and aided in creating his image, just like their symbolic destruction aided in setting the scene - but he still misses them and he knows why. Wear a mask for so long and it stops being one. After all, the best lies are based on truth, or learn to become truth - he knows it better than anyone. Which doesn't stop him from still missing his glasses.
6. For a supposedly subtle manipulator type he enjoys his destructive kido far too much. While he wasn't exactly disappointed with his supposed shikai, he made sure to offset the loss of explosive power by learning more destructive Kido in his first year as a shinigami than any junior death god before him. His love of destructive kido is also the reason why he prefers to use them without any chant - it allows him to appreciate the effects that much more without some pesky distractions.
7. Aizen likes to gloat, though he doesn't call it that way. He knows that it can sometimes leave him wide open, like during the time Yoruichi and Soi Fong almost decapitated him, but he does it anyway. After all, what is the use of setting the scene and crafting a play if you can't enjoy it to the fullest?
8. He didn't have any prodigal talent in the academy, nor a superb potential in kido. He didn't show the raw ability in hakuda or genius zanjutsu and his reiatsu was only slightly above average during the academy days, rising steadily as it should due to the hard work. But contrary to his fellow shinigami Aizen Sousuke never stopped improving, never let the curiosity and wonder of his own abilities to fall into the tired drag of routine. In the end that proved to be his greatest power and the Soul Society's greatest problem.
9. Aizen knew that he and Urahara are the two sides of the same coin the moment he met him. He also understood that out of any of his opponents, Kisuke would be the single most dangerous one. They both never ceased to improve, both craved change. But while Aizen manipulated the surroundings when needed, Urahara cheerfully smashed or re-modeled the world with a smile until it fit him. They both did it for their own, selfish vision though Aizen still doesn't know what Kisuke's vision really is and doubts the crackpot scientist knows it himself. He doubts that Urahara cares either.
10. He is merciless. Not that he is a sadist like Gin, or obsessed with the letter of the law like Yamamoto. It is simply because anyone who goes against him should be ready to pay the same price as he does and he will not grant others any luxury.
11.He isn't infallible and despite his ego he knows it well. That is okay, though - failures sometimes teach you more than success, after all. As long as something new is gained, the game was worth it as far he is concerned.
12.The word 'impossible' is something that can irritate him like few things can. As far as he is concerned there is no such thing as impossible, and those tossing it around frequently are just making excuses for their own lack of ability and determination. Though even he would admit that there are things that are rather improbable and could be labeled as impossible by the weak willed.
13. For that very same reason, he allows for the weaker arancar to strive for position in the Espada. After all, if they won they more than proved their ability to him regardless of their power or status. Gin once joked that Aizen would give the position of an Espada even to Ichigo, had he come by. Aizen just smiled.
14. When he learned of Neliel's resurgence he couldn't help but smirk. After all, an individual of great power was one thing - but a protector of Kurosaki Ichigo's nature gathering his own Espada was just amusing. He doubted the boy even knew what he had done, but still - you just had to appreciate the irony. Who knows, maybe Ichigo could carve his own piece of Hueco Mundo one of those days? He was certainly surrounded by enough power to do so.
15. He respects his opponents. After all, they enter his stage willingly and provide him both means and actors, not to mention serve to keep his resources in top condition. They do deserve some gratitude for that service alone. Doesn't mean he won't crush them without any shred of mercy when they stop being useful though.
16. There is one master in Los Noches and that's Aizen. For all their bickering, jockeying for power and backstabbing among the ranks, arancar learn that lesson or face oblivion. Or worse. After all, Aizen knows the value of fear as an effective tool of management.
17. The only regret about moving up his timetable is the fact he didn't manage to spend more time with Orihime. The girl is truly fascinating to him, and not just because of her powers. Her unique personality really amused him, as did the uneasiness of some of his arancar around the young woman. It was a pity he didn't meet her earlier - she'd have made far better lieutenant than Tousen ever did with some coaching.
18. He is not afraid of death, whenever be it by kido, zanpakuto or anything else. His allies and enemies alike think it is a sign of arrogance, that he simply doesn't believe that he can lose. That is not exactly true. As far as Aizen is concerned, there is no free lunch. His place at the cosmic table came at a price and he is ready to pay it when all is said and done. It was more than worth it and he has no regrets about the chosen course. Of course if he wins he won't need to pay at all, and that is an incentive if there ever was one.
19. He never had role models, he never had idols, he never envied or emulated anyone. He is Aizen Sousuke and he has his own path to walk. He doesn't need anyone else to show him the way. For Aizen, it is both the destination and the journey that matter.
20. Why does he want to be god? Because he can. That by itself is enough of an incentive as far as Aizen is concerned.