Some of the opinions on Reina here are bizarre.
He was world class, or at worst borderline world class (he was #2 behind Casillas for Spain, ahead of Barca's Valdes), certainly at his peak. His clean sheet record alone should tell you that.
Is he going to get into the pantheon of all time great keepers? No, not a chance. Not even for Liverpool by all accounts (maybe as a sub for first team or starting/sub for second team). Was he the best keeper in the Premier League during his time? No, any sane football follower, Liverpool fan or otherwise, would rate Cech and Van der Sar higher, but he was just behind them and not by too much.
Yes he had a mistake or two in him every season (for some reason I always seem to recall him making mistakes vs Everton - except for the final vs West Ham), so not that different to Alisson - it happens, even to the very best.
But he was a top shot stopper (won us many a game, and great with penalties) but more importantly, was very, very quick off his line to anticipate any through balls (someone else made that point very well - we had a team with Finna/Arbeloa, Carragher/Skrtel/Agger/Hyypia, Riise/Aurelio - none particularly quick - playing a relatively high line), and also ridiculously good with the ball at his feet (was probably the best keeper in the world for that at the time).
He was also a leader, and gave the backline the confidence they needed. In fact, Alisson reminds me a lot of him - probably better with the ball literally at his feet but remains to be seen if his passing/throwing is as good in starting counter attacks.
The issue with Reina is that his demise at Liverpool was greatly exaggerated - a lot like Alonso's (Alonso came back with a storming final year though of course). Reina was genuinely poor for a while (longer than Alonso was) and everything near post seemed to go through, but he came back looking solid before Liverpool's bizarre decision to move him on (for Mignolet of all keepers...). And it's tainted a lot of his legacy, because they exaggerate the TIME he was poor for. Same with Alonso. I've heard people say "Alonso was poor for 3 or 4 seasons" which would mean he had basically one great season at Liverpool which is absolute nonsense. He had one poor season (relatively speaking of course) and one season where he played well but it was also injury hit and he had some trouble coming back into form from a long absence and a slightly newer system but adjusted well enough.
Likewise with Reina, I've heard people say he was poor for 3 or 4 seasons, again nonsense. Much like Xabi, he had 1 genuinely poor year, and another where he was looking like he was finding form again before we moved him on.
It's safe to say Reina hasn't hit the heights of his Liverpool career since moving on, but he definitely hasn't been bad either - he's been a pretty decent keeper for Napoli - a very good one for Napoli you could argue actually.
