Dracula's Riddle 1 is an old fashioned linear online riddle game. You solve one riddle, type in the answer in the address bar, and get to the next riddle. This is the game to play if you are of the conservative kind.

Dracula's Riddle 2: Mist of Deceit is more complex than its prequel. The linearity of Dracula's Riddle 1 is not to be found in this game. Here you will often be presented to multiple choice crossroads where you must choose a path to walk. Each path will have its own trail of riddles. Sometimes, in order for a riddle to be solved, you must use a clue or hint that you have found in some other part of the game, perhaps on a different path.

If you are a first time player, Dracula's Riddle 2: Mist of Deceit is the recommended choice. Its riddles and its entire concept is more thought through and will most likely be more entertaining and also challenging.
You will be able to complete Dracula's Riddle 2: Mist of Deceit without having played Dracula's Riddle 1, but the story may be more comprehensible if you have played both games.

Good luck on your quest!