More like the いい in かっこいい literally is the irregular adjective いい. Adjectives that end in いい aren't necessarily the same. Check the kanji (if kanji is given). 可愛い (かわいい) obviously can't be based on 好い/良い
Any decent dictionary will point out the conjugation of adjectives. Although you may have to look up the glossary for that dictionary to find out what the notation means.
WWWJDIC gives かっこいい as (adj-ix) for example.