Compared to TW2, Witcher 1's not great IMO. A clunky combat system and... it just doesn't convey the character's emotions or plot as well as W2 does. The menu systems are also very hard to decipher, as nearly everything looks interactive but this often isn't the case. Granted, this could be due to its age and technical limitations at the time, but I'm going to play W2 a second time after giving up on W1 a couple hours in.
I do enjoy old RPGs (Oblivion, Morrowind, Avernum, Divinity) but W2 is miles and miles better than its predecessor, IMO. If you're just looking to get into the game trilogy in preparation for W3, I'd defo start at W2. I did, and the plot made complete sense in the end despite little knowledge obtained from W1 (in short, you don't miss much if you skip the first game because of its combat or story or whatever).