He criticised the rival companies' software, claiming it is slower and less secure than Oracle's, and said IBM and Microsoft are also more expensive than Oracle.
"Despite what everyone says, our software is actually cheaper," Ellison told delegates. For example, users would have to pay $140,000 (£99,000) for a 500-user licence for Microsoft Exchange running on a four-chip server, he claimed, citing what he said are Microsoft's published prices.
Oracle can offer customers an e-mail server for the same number of users on the same hardware for $80,000, because the Oracle9i database comes bundled with an e-mail server, Ellison added.
Turning to IBM, he said a user would have to pay $272,000 for software to build a portal for 25 users. Oracle bundles portal software with its application server, so users could build a similar portal using Oracle's software for $40,000, he argued.
However, Stan Sorensen, Microsoft's director of enterprise server marketing, said: "It's ironic to hear Larry claim they [Oracle] are price leaders in anything."
The enterprise edition of Microsoft Exchange costs $4,000 per server and then about $60 per desktop, said Sorensen. The price of the software does not change with the number of chips being used, so the system Ellison described could easily be had for less than $40,000, he added.
"If you're paying $140,000 for the system from us, then someone has sold you something you don't need," Sorensen said.
Some users at Openworld were also sceptical of Ellison's claims. "It seems too good to be true," said one Oracle database administrator, adding that Microsoft Exchange features several back-end administrative features built in that may not be available from Oracle's e-mail server.
"Notice he [Ellison] didn't say anything about SQL Server pricing," the administrator added, referring to Microsoft's own database, which competes with Oracle9i.
The delegate said his company currently uses a version of Oracle8i. The features in Oracle9i touted by Oracle would not entice him to upgrade before the company issues a second release of the product, which is due early next year.
"If you do [upgrade] now, you're basically a beta tester for Oracle, helping them clear out all the bugs," he said.
"My concern with Oracle is: how much does it cost to use all of this?" said another delegate. The Oracle9i database and application server are "inclusive and well-packaged", but hiring staff that can figure out how to use all the features could prove expensive, he added.
A third delegate said performance benchmarks highlighted by Ellison for Oracle's database and application server looked impressive, but he wondered how many customers use the software for the types of applications tested.
"The benchmarks do look better, but you wonder how many customers they really apply to," he said. "Do many people need to run 4,000 transactions per second?"
Ellison maintained that customers would do better if they stopped using software from Microsoft, IBM and their partners, and switched to an Oracle stack composed of its database, application server and business applications.
He cited a series of benchmark tests intended to show that Oracle's application server runs faster than those of IBM and BEA Systems, and also said Oracle's software is "unbreakable" when used in clustered configurations.