First, no, the Big Red Machine wasn't one of the greatest offenses of all time. It was a very good offense. With a 108 OPS+. There's are one or two teams like that every single season.
But just for fun, let's compare the batting orders (the positions will scramble, because our strengths lie in different areas, to a certain extent, but the batting order slots line up favorably)
Position - Red (OPS) - Mariner (OPS Proj) - WINNER
1) Rose (132) - Segura (130) - PUSH (pretty similar hitters too)
2) Griffey (119) - Haniger (130) - SEA (Griffey Sr. with power...LOL)
3) Morgan (169) - Cano (135) - CIN
4) Bench (140) - Cruz (150) - SEA
5) Perez (124) - Seager (115) - PUSH (Seager got off to a slow start this year, but the two are very similar players)
6) Foster (139) - Valencia (110) - CIN
7) Concepcion (87) - Gamel/Heredia (115) - SEA
8) Geronimo (90) - Zunino (95) - PUSH
9) Driessen/Rettenmund/Plummer (75) - Dyson (95) - SEA
The 9 hole had a bunch of pitchers hitting for Cincy, but they let the benchies play a lot so I decided to make that comparison. That Reds team was more front-loaded than we are...we are deeper than they were...deeper and more balanced (with more power).