What are some alternatives?
When comparing Rocksmith and Piano Notes Fun, you can also consider the following products
Frets on Fire - Bonus content.
Yousician - An interactive guitar-learning app.
Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Simply Piano - Fast and fun way to learn piano
Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.