A wise choice, VII is a brilliant game

Some of them are similar like VI and IX as AG has pointed out, but the rest are drastically different as far as story, theme and game play goes.

The best advice I could give, is to read a brief synopsis on each game that won't spoil the story and see what appeals to you the most.

All of the titles that have been recommended so far are great games, but I also recommend that you give VIII thought as well. VIII is drastically different with a much more modern theme to it and an excellent game in my opinion. Definitely worth a play through, especially if you're new to FF.