When Michael left Michael was the heart of the show and why it was able to obtain such a huge following. Although it was able to have some pretty strong episodes after his departure, it was never the same. A massive reason behind this was the show's inability to find a strong enough replacement as boss of Dunder Mifflin.
There were plenty of better options that they could have gone with. Some characters deserved it due to their strong work, while others would have been hilarious in the role due to their personalities. Whatever the case may be, it was rather disappointing to see the series go into the direction they went, or better yet, lack thereof.
Taking a deeper look into some potential replacement options helps shine a light on this fact greatly.
Dwight
Dwight really should have been the boss as soon as Michael left. He was the employee who was the most dedicated to the company and was an excellent worker overall. He also was Michael's right-hand man, so he knew what it took to be a good boss.
The primary flaw that Dwight had was his inability to relate to others. This was especially the case in earlier seasons, but it should be noted that he was far better at this later on. Overall, he would have been a marvelous boss to help the company.
Jim
Although Jim was known for his relaxed personality, he did also have strong leadership qualities. He was a very empathetic person who was marvelous at his job when he tried. Also, he was well-received throughout the office for his coolness.
Ideally, a tag team between Dwight and Jim would have been a nice way to go as Michael's replacement. The two's opposing qualities would actually have been marvelous for the branch, especially when seeing as how they were able to form a strong friendship later on.
Pam
Pam's growth as a character was truly spectacular. She became far more confident in herself as the series progressed, which would result in her being promoted within the company. One could even argue that she could have been a great boss.
Her true leadership qualities were mostly displayed when she began working for the short-lived Michael Scott Paper Company. She also showed that she did have skills in sales, while also being a lot tougher than others may have assumed. Overall, it would be hard to not at least consider her.
Oscar
Oscar was an immensely intelligent character, so one could say he could have been a solid character to run the office. In of entertainment, it could have been hilarious, as he would have had to deal with a lot of unique characters.
The primary worry of Oscar running the company would be his pretentiousness. Although he was smart, he also would put others down often. This could have been a bit of an issue for morale, but overall, Oscar would still have been interesting in the position.
Toby
Toby would have an interesting option as boss. He was the head of HR, so he certainly possessed a lot of empathy for the people working there. He also knew them all quite well, so taking on this role may not have been too challenging for him.
Toby was a bit on the nicer side, so everyone probably would have been content with him running Dunder Mifflin. Michael, on the other hand, likely would have done everything in his power to not allow this to occur, of course.
Meredith
Meredith becoming the boss would have been absolutely bananas. She was the prime example of somebody who liked to party, as evidenced by her many antics while working. However, she also possessed a high degree of intelligence, as it would be revealed that she received her Ph.D.
Realistically, that could have actually been used in her favor, had she wanted the position. Yet, this was not revealed until the end of the series. Overall, for humor purposes, she could have been a marvelous choice to go with.
Creed
In of pure hilarity, Creed would have been a marvelous choice to replace Michael. He had been working there for the longest amount of time, so realistically, it would have made sense for him to take on this position permanently.
Of course, his involvement in illegal activities would have been certainly problematic to say the least. Yet, even with this being the case, it would have been excellent for the show to take an extended look at this possibility.
Charles
Charles had already been the boss during his short stint with the series. He definitely knew how to run it, as his no-nonsense approach would result in the company doing quite well under his watch.
Even more interestingly, it would have been quite intriguing to see his ongoing feud with Jim. Of course, it was one-sided, as Jim had worked extremely hard to get Charles to like him, but to no avail. Seeing this explored more could have provided a lot of funny moments.
Angela
Angela was one of the toughest characters in this series. Therefore, she definitely could have held her own as a boss. It may have been hard for the others though, as she had many moments of being quite off-putting.
This could have created a lot of conflict in the series, which of course, would have brought upon a high amount of laughs. At a minimum, she should have at least been considered, giving her long tenure with the company.
Kevin
Kevin running the company would have been as chaotic as it would have been hilarious. Kevin was a man who made a plethora of mistakes throughout the shows run, as his intelligence was significantly lower than the rest of the bunch.
Yet, with him running the show, he would have been able to provide his workers with his famous chili whenever he wanted. That certainly would have been stellar for morale, as long as he didn't spill it everywhere like before. However, the company may have suffered severely with him in charge because of his decision making.