How should someone who likes the big, stirring works of the Romantic era approach Mozart? Mozart's music brims with melody, he could not by any stretch of the imagination be described as 'difficult'.
Nevertheless, tastes differ, and for someone enamoured with the Romantics, I would imagine that the difficulty lay in adjusting to the scale of the music of the Classical period, which is much narrower in terms of sound.
Perhaps the most dramatic of his works are his operas so excerpts such as the overture to the Magic Flute and Figaro would make a good beginning for someone wanting to explore.
If sufficient interest is aroused, then perhaps the delightful Flute and Harp concerto, and the Sinfonia Concertante for Violin and Viola could be attempted. After that the piano concerti, starting with No.14.
For an absolute beginner, what better way to dip ones fingers in than with Eine Kleine Nachmusik. Go on, give it a try, its a lot easier to listen to than to pronounce.