Cichlids are good for beginners. Someday though make sure you check out the more rare exciting fish too. Ive had convicts, firemouths, JDs, Green Terrors etc that all were cool but didnt hold my intrest very long. However if you can get a larger tank I would definatley recomend an Oscar! They have soo much personality.
Other cool options for that tank would be polypterous, eels, smaller cats, Green Spotted Puffer (Will need to be brackish), knife fish, FW barracuda, and all kinds of other interesting carnivors.
One last thing because you sound like you are new to fish keeping. Make sure you resaerch and fully understand tank cycling as well as the basics of mechanical, chemical, and bio filtration.