What are the top 5 football/soccer teams in the world?

Depends on what you mean by "top teams".

For on the pitch performance, FOX Sports compiles a bi-weekly list based on votes from writers and commentators. Here's their latest rankings as of this posting:
1) Manchester United
2) Olympique Lyon
3) Chelsea FC
4) Internazionale Milan
5) FC Barcelona
http://msn.foxsports.com/soccer/story/3412562
For the most part, ranking teams based on their performances on the field is a matter of opinion.

Other rankings:
-- Highest income (as listed in February 2006)
http://news.bbc.co.uk/2/hi/business/4716174.stm
-- Highest average attendences
http://www.geocities.com/worldfootballrankings2004/Top125SoccerClubs.html

i think ou have to look at the history of the club as well as their present winnings, which makes me feel that Liverpool FC has to be up there. Its also the reason i dont rate Chelsea so we'll leave them out for now. Manchester United
have to be up there. They dominated the best league in the world (in my opinion) for ages so they are definately up there. Arsenal FC are a bit up and down. The only club ever to go un-beaten in a season but have had a dip at the moment so like their London Neighbours Arsenal miss out.

The 2 obvious teams from Spain are Real Madrid and Barcelona. They have dominated the Spanish league for years now and are serial under achievers in the big cups! so those to go in.

Now for the difficult last team. Lyon is a nice idea but i think for the standard of league they are in its no suprise they dominate it and they have never done that well in Champions league. For me the last team to go in is AC Milan. Despite last years altecation with match fixing reports, AC have always been a major player in both Europe and Italy.

So my top 5 are:
Manchester UTD
Barcelona
Liverpool
AC Milan
Real Madrid

I think it would have to go:

1 Germany
2 Portugal
3 Brasil
4 Mexico
5 Argentina

Based on who they have on the team. (experience, wins to loss columns, etc.)

As of now (24 October 2007)

1. Arsenal
2. Arsenal 'B'
3. Arsenal Ladies
4. Arsenal reserves
5. Arsenal youth team

Everyone has their opinions, but my top 5 teams in the world are:
1) Inter Milan
2) Barcelona
3) Manchester United
4) Bayern Munchen
5) Tottenham Hotspur ( thats right)

The most storied in the last 20 years in the top tier leagues are:

1. FC Barcelona
2. Manchester United
3. AC Milan
4. Ajax Amsterdam
5. Bayern Munich
Sleepers : Chelsea,Liverpool,Juventus,Celtic,Aston Villa,Real Madrid,Inter Milan,PSV.

if you really look at the history of the clubs then you should take a look at the track record of the clubs how many times they won since the european cups/chapions league was instated. The track record reads:
1. Real Madrid 7. times
2. AC Milan 6. times
3. Liverpool 4. times
4. Bayern Munchen 4. times
5. Ajax 4. times

Including european cup 2 or uefa would perhaps change the ranking, but its all about being the best in class what counts isnt it?

1. real Madrid
2. AC milan
3. Bayern Munchen
4. Liverpool
5. Ajax

depends on a number of things like finance,fanatical support,size of stadia and many other things

Based on realistic conclusions:
1. AC MILAN
2.BOCA JUNIORS
3.REAL MADRID
4.MANCHESTER UNITED
5.BAYERN MUNCHEN

countries:
germany
brazil
argentina
greece
portugal

clubs:
arsenal
man.united
olympiakos
aek athens
juventus

at this present time, in no particular order
id go with man utd, arsenal, real madrid, inter milan. unfortunately, id like to say ac milan, but their form really sucks atm, so i cant really think of a 5th, but those 4 are definitely tops, 5th maybe to kop/juve/barca one of those powerhouses who are just arent in as good form as united and arsenal

liverpool
man u
barca
boca jnrs
chelsea

manchester united, barcelona fc, liverpool fc, real madrid,ac milan

no brazilian teams...where do you guys think the best players in the world come from..........gremio, corinthians, sao paulo?...not to mention the first three club world soccer cup winners came from brazil?..and finally the last two years its been europeans m.united and liverpool...but who are the runners up to them las two year a brazilian team and an argentinian team...it means nothing to win the champions league 100 times if you loose the club world cup every time.

1 Real Madrid (Biggest club in the world, hands down)
2 FC Barcelona
3 Manchester United
4 Liverpool
5 Milan

For top stadiums check:
http://tenalicio.us/sports/soccer-stadium.html

1. Barcelona FC (Spain)
2. Inter Milan (Italy)
3.Chelsea FC (England)
4.Fenerbahce (Turkey)
5.Bayern Munchen (Germany)