I thought I'd do a quick little study myself. I calculated actual team runs scored above NL average and runs allowed above NL average, after park factor correction, from 1890-2008 (ok, so I only have park factors for 1901+ teams). For 2009, I did the same, but I extrapolated to 162 games to make the data comparable.
By using park factors and the NL Average baseline, I should be correcting for pretty much everything aside from level of competition. Also note that I'm strictly using actual runs data--no RC, lwts, BsR, DIPS, UZR, etc. I love looking at components because they're less noisy (e.g. the BtB Power Rankings), but you also risk losing some information that the component stats don't take into account. So, for that reason, I think it makes the most sense to just start with straight up RS and RA.
Anyway, here are those data graphically.
Above-average is good on both offense and defense. The line is a 10-year moving average, because there are huge year-to-year fluctuations.
The past decade excepted, the Reds have traditionally had good defense (meaning pitching + fielding). Offensively, there really are only a few times when they've consistently posted above-average hitting clubs--though you can clearly see how remarkable the Big Red Machine era was (those two little dots blue dots near the top of the graph are runs scored above average in 1975 and 1976...man oh man). Since then, the Reds have basically fluctuated around average on offense.
As far as best- and worst-offensive seasons go, here you are:
Top-10 Reds Offenses
Also, I think I remember there were a lot of complaints about too many home runs in 2005. Remember those days? :)
Worst-10 Reds Offenses
And holy crap, that 1930 team was horrible. Harry Heilmann hit 0.333/0.416/0.577 for that team, but there wasn't much of a supporting cast. They won 59 games.
Top-10 Reds Defenses
If you glance back up at the graph, there were two large peaks in Reds' defense in the '20s and in the '40s, and you see some of that in this table. The 1890's also had some brilliant defenses, including probably their best defensive team ever in 1896. The 1940 team included Bucky Walters and Paul Derringer in the rotation, and won the World Series over the Tigers.
And two of the last three Reds teams to make the post-season (I count the 1-game playoff against the Mets in '99 postseason, technicalities be damned!) are on this list. Big Red Machine teams don't appear, though the '75 team ranks 18th.
Worst-10 Reds Defenses
One last thing. Since I had the data in front of me, I calculated PythagenPat-estimated winning percentages for all Reds teams since 1890. Through last night's game, the Reds have been outscored 81743-81634 since 1890, which results in a PythagenPat of 0.4994 since they joined the National League.
Top-10 PythagenPat Winning % Reds Teams
Big Red Machine at the top, naturally.
That 1919 team is interesting, as they were, of course, the "victims" (benefactors?) of the Black Sox scandal. The story you always hear is that the Reds were a vastly inferior team to the Sox, and how the Sox gave the series away. Maybe they did, but if they played to the best of their abilities, I wouldn't be surprised to see this Reds team still beat them. They were a very, very good team.
I was also surprised to see three teams from the mid-late '90's on this list (though I cheated a bit to get them on there again). The '99 team is a favorite of mine, but the '94 and '95 teams were superb as well. Both years were shortened seasons, so they might have posted even higher numbers vs. average had they played 162 games both years. Damned strike.
Worst-10 PythagenPat W% Reds Teams
The '39 and '40 teams must have been incredibly special to this town. It's before my time, though, and I'm just starting to learn about those players and teams.
For the record, 2009 is on pace to be the 20th-worst team in Reds history.
Almost all raw data is from the Baseball Databank.