How are Jack and Algernon similar to and different from each other in The Importance of Being Earnest?
Jack and Algernon are similar in that they are both liars. They have each created a fictitious individual who is meant to help them escape social obligations. When Jack gets tired of being the upstanding guardian to an impressionable young woman, his ward Cecily, he makes up some story about his dissolute "younger brother," Ernest. He talks a great deal about the high moral tone he must adopt in his role as guardian, and yet he hypocritically lies about a brother so that he can go into town and act badly. When Algernon cannot stand being with his overbearing Aunt Augusta and attending the various social functions upon which she insists, he claims that he must, instead, visit his ailing, invalid friend, Bunbury. In other words, both men chafe against their social and familial obligations, and they deal with their frustrations by lying to escape such responsibilities.
One might say that Algernon is just a bit more clever than Jack. Algernon masterminds a visit to Jack's country home so that he can meet and woo Cecily: a scheme which is quite successful. Jack, however, has more actual money than Algernon. Though Algernon is a gentleman, we learn that he really has little by way of "ready money," as his butler puts it, and Jack -- a foundling -- ironically has quite a bit more cash than the bred gentleman, Algernon.
Jack and Algernon are similar in that they are both determined and committed to please the women they love. For instance, they are both willing and even make plans with the Reverend to change their names to Ernest so they can be accepted by the women they love.
They are both escapists, as seen when they create fictitious characters in order to avoid facing tough circumstances. Algernon invents Bunbury, a fictitious friend, so he can always have a reason to escape his aunt, Augusta. On the other hand, Jack invents a fictitious brother named Ernest, to facilitate his escape from Cecily and her governess.
The difference between the two emanates from their different upbringing. Jack was raised by a benefactor who found him abandoned at the station while Algernon was raised by his aristocratic family.