Superlative x Comparative

Theory
http://esl.about.com/cs/beginner/a/beg_compsup.htm

Games
https://learnenglishkids.britishcouncil.org/en/grammar-games/comparatives-and-superlatives

Exercises
http://www.englisch-hilfen.de/en/exercises/adjectives_adverbs/adjectives_comparison_sentences2.htm
http://www.ego4u.com/en/cram-up/grammar/adjectives-adverbs/adjectives/exercises
http://www.usingenglish.com/quizzes/45.html
http://www.eclecticenglish.com/quizzes/ComparativeQuiz/comparativeQuiz.html
http://www.learnenglishfeelgood.com/english-comparative-superlative1.html