I agree with Ryan in terms of the idea of keeping a lone cichlid if you cater for its and its tankmates needs. And those needs can be as diverse as fishkeeping itself. Look at requirements of your fish, the size it will grow, ph needs. etc. etc. A dwarf cichlid can be a great member of a community tank, as can a huge Oscar with a big plec and an Arowana, or an Angel in a school of tetras and a bottom full of catfish. Most of the African species we get here (excluding some of the river fish) are cichlids, but one only of a species is not uncommon in Rift display tank. Tropheus, Frontosa's are more of the school fish but will survive alone as long as the tankmates can do likewise.
To paraphrase David R-Not all cichlids are created equal.