"the giants are among the top 10 most valuable American companies of any kind." Depends what you mean by "value". If current price Mr Market is willing to pay

"the giants are among the top 10 most valuable American companies of any kind." Depends what you mean by "value". If current price Mr Market is willing to pay = "value" then yes. If value is a measure of long term return based on another set of measures like profitability etc then basing the future dominance of these companies on their current stock price seems a little speculative.