I'll get in on this.
1. Led Zepplin
2. Yes
3. Kansas
4. Rush
5. Tool
Picking 6-10 would be much tougher, as there are many that are worthy. To name a few - Boston, Black Sabbath, Pearl Jam, Soundgarden/Audioslave, Korn, Radiohead, Dire Straits, Pink Floyd, The Who, The Stones, Allman Brothers, SRV, The Doors, ELP, Red Hot Chili Peppers, Queen, Live, Genesis, Dave Matthews Band, ACDC, Santana, etc. etc. etc.