Bale's contribution might be underappreciated, but I don't like the way this comparison is presented.
Balance in club football changed: La Liga was way more competitive and general stats inflation. In addition they don't even played the same roles.
That's true. Just having a look at the league table in those years one can conclude that league was a nightmare to play in.
Take a look at the 2001/02 season for example.
The top scorers at the end of the season are:
Real Madrid: 69 goals
Barcelona: 65 goals
Deportivo: 65 goals
Celta de Vigo: 64 goals
The team finishing in the last position manages to get at least one point in half of its games: Zaragoza, 9 W, 10 D, 19 L.
Valencia, who finish first, get only 75 points, and score just 51 goals.
All of Madrid, Barcelona, Deportivo and Celta lose 10 league games during the season. Valencia only lose 5 but also get 12 draws.
At Real Madrid Bale has played in teams scoring 104, 118, 110, 106 and 94 in the league his first 5 seasons.
Having said this, Bale's contribution has been very good no matter what, so I agree completely with you there.