What was the best ever guitar riff in a song?

Determining the "best" guitar riff in a song is subjective and can vary widely depending on personal taste and musical preference. However, some iconic guitar riffs frequently cited as among the best include:

**“Smoke on the Water” by Deep Purple** - Known for its simple and catchy riff, it's often one of the first riffs learned by beginner guitarists.
**“Satisfaction” by The Rolling Stones** - A defining riff in rock music that has stood the test of time.
**“Stairway to Heaven” by Led Zeppelin** - Features a beautiful progression that has captivated listeners for decades.
**“Whole Lotta Love” by Led Zeppelin** - Famous for its heavy and unmistakable riff.
**“Sweet Child o' Mine” by Guns N' Roses** - The opening riff is instantly recognizable and has a melodic quality.
**“Seven Nation Army” by The White Stripes** - Its simplicity and anthemic quality have made it a staple at live events and sports arenas.

Ultimately, the "best" riff can be a matter of personal opinion, influenced by nostalgia, genre preferences, and exposure to different types of music.