Over the last 10 years it's Neuer easy, though he looks like he's declined badly now after the injury. Ter Stegen and Alisson have been the 2 best in the last 20 months or so for me. I rate Oblak a lot too but he's crap with the ball and I'd like to see him exposed a bit more rather than an 11 man defence, he pretty much never has to sweep or anything. Ter Stegen is pretty much excellent at everything and though his shot stopping numbers aren't amazing he has Dave's thing of super man type saves at big moments. Alisson has posted obscene save per goal numbers for 2 years, he might be behind a good defence now but at Roma last season it was like a siege on their goal every game and he saved everything, now they've got a shit goalie they let loads in again. He's also obviously good with the ball, decent on crosses, excellent sweeping.
And you are right, everyone makes mistakes, including the ones I've listed but I think way too many are creeping in to Dave's game at the moment. In the last month alone we've the goal he cost us v PSG, come out minutes later as he knew he'd fecked up, fecked up again and luckily they missed, was ropey on both goals v Southampton, the dodgy punch at the end of the second leg and whatever the hell he was doing for their first yesterday.
I like Dave and there's not loads I'd swap him for but it feels like he just has one really good attribute which some seasons is amazing, that's great but for best in the world convo's I think he needs something extra. He's kinda like the strikers who can only score goals and do pretty much nothing else, it's a quality attribute but to be the best you are going to need more to your game.