I never remember where all the different generations start and stop, but my parents are slightly pre Baby-Boomer (born in '43 and '44). I think I'm a Gen-Xer (my brother was born in '63, I was born in '68 and my sister in '69)?
Mostly, my parents were really great.
My dad's biggest "mistake" was/is being an alcoholic. He was an amazing dad when I was little. But, he couldn't handle it when my sister and I hit puberty, and his drinking was esclating. By the time I was about 14, he'd pretty much checked out of our family, emotionally. He'd stay at the bar drinking, after work, sometimes until bedtime. When he was home, he wasn't involved with anything - mostly just sat and watched tv and drank beer. He wasn't violent, or abusive. He was just completely checked out. At the time, I didn't even really notice, but looking back - he really wasn't part of my adolescence at all. He rarely even interacted with us (Christmas was always nice, at least - I think that's one of te reasons I love it so much). He was also pretty oblivious to hurt feelings and when he was being annoying or irritating (dad was a "funny" drunk, which was amazingly tedious).
I'm not really sure what effect that all had on me, but I think it probably contributed to me falling head over heels for my ex (met when I was 16, and stayed together until I was 31), because my ex was interested in me, talked to me, etc. When I look back, he and I were kind of over the top, in terms of near constant contact, putting each other ahead of everything else, etc. I also think I'm a little oversensitive to feeling as though I'm being ignored.
Mom made two big mistakes, in my opinion (and hers). The first was not cutting off contact with her incredibly toxic mother. That woman did pretty serious damage to all of her grandchildren (I consider myself a borderline basketcase, and I'm probably one of the two most functional of the six of us). Mom saw it, but not clearly, and really believed that "kids need their grandparents". If she could do it over again, she'd have cut off contact when I was very little. Effects? Too wide ranging to really describe. Grandma had a very negative impact on me on almost all levels. The crap that went on in her house (sexual abuse from my grandfather and a bribe of silence in the form of junk food) triggered disordered eating that I've struggled with most of my life. I don't eat crap to feel good, or to "stuff" - I eat crap as a form of slow suicide, and I know it when I'm doing it...I just don't care. (I'm on an up right now, and sugar isn't an issue, but major stresses in my life end up in a pile of sugar - the end of my first marriage, c-section related trauma, and Aaron's death have all triggered it.)
Mom's second big mistake was staying with my dad. She got really wrapped up in the relationship, and unwilling to end it. She used to go to the bar occasionally to confront him, and spent more hours than I care to think about sitting at home fretting about when he'd come back. She wasn't a neglectful parent, but she was also human, and only had so much time and energy to go around. We all needed more of those than she had to spare. I was a screwed up mess, and my sister went completely off the skids. Mom just wasn't able to deal with it all, and try to force things to work with my dad. (When they finally split up for good, I was in my early 20s, and was just soooo relieved that they'd finally ended it.) I can't really blame her for desperately wanting her marriage to work, especially since it was an unusually good relationship in the early days, but it definitely had a negative impact on her parenting.
Mom also made one more minor, but....fundamental?...mistake. She was too critical. I don't think she ever realized it, and I only realized it myself a few years ago. But, she was very prone to pointing out what we'd done wrong, without enough emphasis on what we'd done right. I find myself doing it sometimes, too. She was (is) kind of prone to making random critical comments about public figures - the way they look, the way they dress, whatever. I think it's kind of obnoxious, and I hope I don't do it, but I probably do, to some degree. :(
I think this one is a generational improvement thing. My mom was nowhere near as bad as her mom, and I'm not as bad as my mom. We'll see what my kids are like. The criticism definitely impacted me. In conjuction with my peer issues (too numerous to mention), inability to fit in anywhere (my social circle with my ex was my haven - the first place in my life where I felt as if I belonged - and it really wasn't a healthy dynamic, but I couldn't resist it), and my grandmother's incessant emphasis on modesty (not in dress, but in the sense of humility - in it was a major sin to be proud of myself for anything), the criticism left me with about the same level of self-confidence as the average peanut.
Mom made one other mistake, but it didn't affect me. She didn't take her children's temperaments into account when she was approaching discipline. It didn't matter to me very much, because her approach was right for me. I think it was really hard on my sister, though, because my sister had different needs than mom or I did. (One of the biggies is that it was really important to my sister to fit in. I don't think mom should have broken the bank or gone to extremes to facilitate that, but she mostly just dismissed it, because it wasn't important to her, so she felt it shouldn't be important to anyone. I think she'd do things differently now.)
And, despite all that - they were great. Dad was an amazingly involved dad, especially for the time, when we were little. And, they were both really great about spending time with us, letting us do things, and just...letting us be who we were, yk? I always knew we were important to both of them (well, to mom, and to dad until my teens). Most of my friends envied me, and our place was the "hang out" place, because our friends all really liked our parents.