If I had to rank each series:
1. 2004 (Best series, I loved the all final 7 original housemates)
2. 2005 (Amazing series with stand outs like Vesna and Christie)
3. 2001 (Even rewatching it when its 18 years old the authenticity of it is still so clear and enjoyable to watch)
4. 2007 (Under rated, decent cast, I personally found it very enjoyable)
5. 2012 (I actually liked 9s first attempt at Big Brother, decent relatable people and consistency with the format)
6. 2006 (A pretty meh series imo but good cast, decent twists and also enjoyable story lines)
7. 2013 (Pretty good cast for 9, interesting story line however the story line itself I found to be repetitive until the end)
8. 2003 (The only meh series on 10 IMO, loved Reggie however after star housemates like Saxon and Joanne leave its a drag to watch)
9. 2008 (Meh underrated, not that bad, and I personally disagree with the negativity towards the final 3)
10. 2002 (Explained above)
11. 2014 (Worst series)