they aren't really similar, though. I couldn't get into Witcher 1 and 2 at first, either, even though putting some 20-30 hours into each.
I recently replayed Witcher 2 ahead of the release of 3, finally got into it, but I still don't consider it all that special.
Much more than Witcher 1, Witcher 2 is on rails. It basically plays like Call of Duty with swords and magic and blah blah political story about blah blah kingdom doing who-gives-a-turd, really.
Witcher 3 is phenomenal. The political bollocks is there, but it's really quite ancillary to the main story, and the side stories, which are far more personal and far more engaging. It is open-ended, free-roaming, go wherever the hell you want and when you want.
I would honestly recommend people that have tried the first 2 and couldn't get into them, to just forget them all together and go straight to 3. The fighting mechanics aren't horrible, but it does get repetitive after many many hours...but this is true of every game. ...every game. It's very mobile, very fluid, and offers you some choices between 2 main styles that you prefer--sword focused or magic focused, or a bit of both. I find it to be the best use of Witcher's style of combat out of the 3 games, and it removes the tedium of the stupid potion/meditation/alchemy interface from the previous 2 games.
Maybe go back to the first 2 games if you thoroughly enjoy 3 and want more of the background, though I imagine Witcher 1, especially, would be difficult to get into.