It really depends on what club you go to, to be honest. There are some clubs that really are just so strong that their 4s and 5s have some quality young cricketers. But 4s and 5s are definitely not park cricket. Far from it mate. Bowlers tend to be smarter and more clever, whereas batsmen will put away bad balls with a hell of a lot more ease in 4s than in 6s.
2nds and 3rds are a good standard of cricket. Especially in Sydney. Blokes come over all the time that play 1st XI back in England and can't break out of 3rd grade. I played a year of grade at Sydney University and there was a batsman there from Scotland who had played some first class games and several bona fide ODIs for Scotland, yet still couldn't make 1st grade, and spent the season in 2nds. It's a really strong standard.
I realise the talent at Sydney University cricket club, but my opinion is based on 3 seasons of Sydney grade cricket.
I have played grades 1-4.
4s was pretty horrible cricket tbh, altho i only played 3 games of 4's so yeah
2s and 3s was good like i said. It was a level above 4's and 5's (i can imagine). Most players in 2's could probably play at 1st grade level and be able to hold their own. I had more trouble at times, bowling to 2nd grade batsmen as opposed to 1st graders. Everyone knew everyone in 1st grade, and my captain had a plan for every batsmen. Bowling without a set plan to a good batsmen (which i occasionally found myself doing in 2's and 3's), is horribleeee.
1st grade was more of a profession then a sport. The attention that was placed on me even at training was intense. I would often have 3-4 head coaches watching me bowl in the nets on a Tuesday, Thursday, and Friday afternoon. Cricket was suddenly not fun.