Mafia III went really open world and less story driven.
Alot of people like that but it's not for me. I like a good story and I'm happy for that to be on rails. The other thing III did was have lots of "useless" little collectibles about the place...I mean lots and for a gamer like me, they become very, very distracting.
So when I say they got worse, it's obviously from my viewpoint. lots of people, I imagine, who like alot more open world and these collectibles, would've definitely had a different opinion to me.
I don't know what it was specifically or even if it was any one thing...but Mafia for me had me gripped...the other two seemed to "move away" from the original. The second not so much but III definitely seemed to.
The second one was ok and had a great story and living world, but some of the missions were downright lazy...I think there was a 5 or 10 minute mission (could've been longer or shorter) that had you selling cigarettes. Another had you cleaning a urinal...real boring crap that gets put into a game because "gamers need shit to do"...you know? Rather than just having a cinematic, that showed what was going on, we need to keep the gamer moving...so press this key several times to clean left and this key to clean right. Thankfully there weren't many and the second one had a cracking story - particularly and excellent tie in to the first one.
So anyone wanting to play the Mafia games, I'd say play the first one (original or the new one...they're almost identical bar the graphics and some added dialog and cut scenes I think), then play the second and get the tie in to the first one...it was worth it - and try III when it's on sale...but don't expect the ride you had from the first two.
imo