Can't compare NHL with Euro Soccer. Or any other North American major league sport. For starters, in the euro soccer leagues, there is always different tournaments being played all the time (i.e. FA Cup, Champions League, Champions Cup, etc...) In tournaments, such as the FA Cup, all teams take part (from the premiership, all the way down to Division 3) Individual leagues (such as English Premiership, Serie A, etc...) is only one part of the season, the slew of tournaments are another. The individual national leagues are more or less a qualifier to get the the Euro Champions League anyways, which is the Big Prize.
Second, there is no playoffs in these individual leagues, the team with the most points at the end of the season win the cup. There are cups for the top teams in all divisions, not just the Premiership. Besides, the same teams always wins the Premiership anyways, in England, that is ususally Manchester United or Arsenal anyway (they have the most $$$$$), most fans of the other teams know by the first 1/4 of the season that their teams don't have a prayer in taking the top spot yet there is still enthusiasm for the team. If you are near the bottom of the Premiership though, there is interest in whether or not the team gets relegated. There are tournaments in which there teams can play, and as a result, there is always interest. The real playoffs are in the Euro Champions League.
Regarding lower tiered teams, they take part in various tourneys where they play the Big Boys and, usually, end up losing (such as FA cup). Sometimes though, an upset can happen (If I am not mistaken, I believe Manchester United was knocked out of the FA cup by a low level team this past year
)
Another thing to consider is the way contracts work over there. All I know, it's way different. Teams pay for players with cash, not sure about individual contracts, no such thing as trades. Also, Euro soccer leagues are more or less turning into conferences, the european soccer is becoming one huge league (again, the Champions League is the unofficial playoffs)