I don't know exactly what kind of trip you have planned or what you are looking for, but I think you can find whatever it is, but better somewhere else.
I thought the ruins of Palenque, in southern Mexico were similar to but more interesting than Tikal and in a more dramatic setting. The food in Guatemala, after spending 6 weeks in Mexico was much like Mexican food without the flavor.
The people in Honduras and and Nicaragua were friendlier. If you are hoping to an authentic experience those two countries have seen a lot less tourism over the past 20 years and at least feel like you are getting a truer glimpse of Central America, with the same language, topography, culture, food, etc.
If you are looking for a well worn path, Costa Rica is a little more expensive but a lot more comfortable. More jungle tours and beaches than Mayan ruins here, but if part of what you are looking for is meeting other travelers from around the world and having a good time this is a better option.
If I had a couple weeks and were looking to hit this part of the world I'd look to put together an itinerary that did something like one of the following, depending on what I was after.
* Start in Oaxaca spending a couple days exploring the famous food markets there - interesting and different cuising from what you think of as Mexican food. This is the area that roasts grasshoppers but also puts together delicate mole sauces from pumpkin seeds in the fall. The food is varied and delicious and safe to eat in the open air markets. Head down through San Cristobal de las Casas and maybe hit a couple side trips in Chiapas. Spend a day or two near Palenque and find my way home. Central Mexico is highlands. In December this will be a cool weather trip until you get to the jungle down near the Guatemala border.
* Start on the Pacific coast, around Zihuatanejo perhaps, then Chiapas and Palenque. This is the warm weather beach route.
From either of these you could still hit Guatemala if you've got the time. There is a well worn path from Palenque to Lake Atitlan, which was the highlight of Guatemala for me.
* Hit Nicaragua and the Pacific coast of Costa Rica. Mayan ruins of Copan, colonial town of Granada, volcano island of the Lago de Nicaragua, beach in Costa Rica. Jungle tours in either country.
* Panama - couple days in Panama City. Jungle tour in the northeast. A week in Bocas del Toro - a remarkable beach sopt with few tourists. You travel between the islands daily on motorized canoes.